diff --git a/fluent-syntax/src/ast.js b/fluent-syntax/src/ast.js
index 585eb7836..6a1a583db 100644
--- a/fluent-syntax/src/ast.js
+++ b/fluent-syntax/src/ast.js
@@ -19,11 +19,10 @@ class SyntaxNode extends BaseNode {
 }
 
 export class Resource extends SyntaxNode {
-  constructor(body = [], comment = null) {
+  constructor(body = []) {
     super();
     this.type = 'Resource';
     this.body = body;
-    this.comment = comment;
   }
 }
 
@@ -192,20 +191,31 @@ export class Symbol extends Identifier {
   }
 }
 
-export class Comment extends Entry {
+export class BaseComment extends Entry {
   constructor(content) {
     super();
-    this.type = 'Comment';
+    this.type = 'BaseComment';
     this.content = content;
   }
 }
 
-export class Section extends Entry {
-  constructor(name, comment = null) {
-    super();
-    this.type = 'Section';
-    this.name = name;
-    this.comment = comment;
+export class Comment extends BaseComment {
+  constructor(content) {
+    super(content);
+    this.type = 'Comment';
+  }
+}
+
+export class GroupComment extends BaseComment {
+  constructor(content) {
+    super(content);
+    this.type = 'GroupComment';
+  }
+}
+export class ResourceComment extends BaseComment {
+  constructor(content) {
+    super(content);
+    this.type = 'ResourceComment';
   }
 }
 
diff --git a/fluent-syntax/src/ftlstream.js b/fluent-syntax/src/ftlstream.js
index 108794212..0e72671ca 100644
--- a/fluent-syntax/src/ftlstream.js
+++ b/fluent-syntax/src/ftlstream.js
@@ -109,7 +109,7 @@ export class FTLParserStream extends ParserStream {
     return ((cc >= 48 && cc <= 57) || cc === 45); // 0-9
   }
 
-  isPeekNextLineComment() {
+  isPeekNextLineZeroFourStyleComment() {
     if (!this.currentPeekIs('\n')) {
       return false;
     }
@@ -128,6 +128,39 @@ export class FTLParserStream extends ParserStream {
     return false;
   }
 
+  // -1 - any
+  //  0 - comment
+  //  1 - group comment
+  //  2 - resource comment
+  isPeekNextLineComment(level = -1) {
+    if (!this.currentPeekIs('\n')) {
+      return false;
+    }
+
+    let i = 0;
+
+    while (i <= level || (level === -1 && i < 3)) {
+      this.peek();
+      if (!this.currentPeekIs('#')) {
+        if (i !== level && level !== -1) {
+          this.resetPeek();
+          return false;
+        }
+        break;
+      }
+      i++;
+    }
+
+    this.peek();
+    if ([' ', '\n'].includes(this.currentPeek())) {
+      this.resetPeek();
+      return true;
+    }
+
+    this.resetPeek();
+    return false;
+  }
+
   isPeekNextLineVariantStart() {
     if (!this.currentPeekIs('\n')) {
       return false;
diff --git a/fluent-syntax/src/parser.js b/fluent-syntax/src/parser.js
index 6565ffba6..a7e0c906b 100644
--- a/fluent-syntax/src/parser.js
+++ b/fluent-syntax/src/parser.js
@@ -21,7 +21,7 @@ function withSpan(fn) {
     }
 
     // Spans of Messages and Sections should include the attached Comment.
-    if (node.type === 'Message' || node.type === 'Section') {
+    if (node.type === 'Message') {
       if (node.comment !== null) {
         start = node.comment.span.start;
       }
@@ -42,7 +42,7 @@ export default class FluentParser {
 
     // Poor man's decorators.
     [
-      'getComment', 'getSection', 'getMessage', 'getAttribute',
+      'getComment', 'getMessage', 'getAttribute',
       'getIdentifier', 'getVariant', 'getSymbol', 'getNumber', 'getPattern',
       'getTextElement', 'getPlaceable', 'getExpression',
       'getSelectorExpression', 'getCallArg', 'getString', 'getLiteral',
@@ -52,8 +52,6 @@ export default class FluentParser {
   }
 
   parse(source) {
-    let comment = null;
-
     const ps = new FTLParserStream(source);
     ps.skipBlankLines();
 
@@ -62,8 +60,16 @@ export default class FluentParser {
     while (ps.current()) {
       const entry = this.getEntryOrJunk(ps);
 
-      if (entry.type === 'Comment' && entries.length === 0) {
-        comment = entry;
+      if (entry === null) {
+        // That happens when we get a 0.4 style section
+        continue;
+      }
+
+      if (entry.type === 'Comment' &&
+        entry.zeroFourStyle && entries.length === 0) {
+        const comment = new AST.ResourceComment(entry.content);
+        comment.span = entry.span;
+        entries.push(comment);
       } else {
         entries.push(entry);
       }
@@ -72,7 +78,7 @@ export default class FluentParser {
       ps.skipBlankLines();
     }
 
-    const res = new AST.Resource(entries, comment);
+    const res = new AST.Resource(entries);
 
     if (this.withSpans) {
       res.addSpan(0, ps.getIndex());
@@ -117,7 +123,7 @@ export default class FluentParser {
   getEntry(ps) {
     let comment;
 
-    if (ps.currentIs('/')) {
+    if (ps.currentIs('/') || ps.currentIs('#')) {
       comment = this.getComment(ps);
 
       // The Comment content doesn't include the trailing newline. Consume
@@ -127,20 +133,25 @@ export default class FluentParser {
     }
 
     if (ps.currentIs('[')) {
-      return this.getSection(ps, comment);
+      this.skipSection(ps);
+      if (comment) {
+        return new AST.GroupComment(comment.content);
+      }
+      return null;
     }
 
-    if (ps.isIDStart()) {
+    if (ps.isIDStart() && (!comment || comment.type === 'Comment')) {
       return this.getMessage(ps, comment);
     }
 
     if (comment) {
       return comment;
     }
+
     throw new ParseError('E0002');
   }
 
-  getComment(ps) {
+  getZeroFourStyleComment(ps) {
     ps.expectChar('/');
     ps.expectChar('/');
     ps.takeCharIf(' ');
@@ -153,7 +164,7 @@ export default class FluentParser {
         content += ch;
       }
 
-      if (ps.isPeekNextLineComment()) {
+      if (ps.isPeekNextLineZeroFourStyleComment()) {
         content += '\n';
         ps.next();
         ps.expectChar('/');
@@ -163,23 +174,80 @@ export default class FluentParser {
         break;
       }
     }
-    return new AST.Comment(content);
+
+    const comment = new AST.Comment(content);
+    comment.zeroFourStyle = true;
+    return comment;
   }
 
-  getSection(ps, comment) {
+  getComment(ps) {
+    if (ps.currentIs('/')) {
+      return this.getZeroFourStyleComment(ps);
+    }
+
+    // 0 - comment
+    // 1 - group comment
+    // 2 - resource comment
+    let level = -1;
+    let content = '';
+
+    while (true) {
+      let i = -1;
+      while (ps.currentIs('#') && (i < (level === -1 ? 2 : level))) {
+        ps.next();
+        i++;
+      }
+
+      if (level === -1) {
+        level = i;
+      }
+
+      if (!ps.currentIs('\n')) {
+        ps.expectChar(' ');
+        let ch;
+        while ((ch = ps.takeChar(x => x !== '\n'))) {
+          content += ch;
+        }
+      }
+
+      if (ps.isPeekNextLineComment(level, false)) {
+        content += '\n';
+        ps.next();
+      } else {
+        break;
+      }
+    }
+
+    let Comment;
+    switch (level) {
+      case 0:
+        Comment = AST.Comment;
+        break;
+      case 1:
+        Comment = AST.GroupComment;
+        break;
+      case 2:
+        Comment = AST.ResourceComment;
+        break;
+    }
+    return new Comment(content);
+  }
+
+  skipSection(ps) {
     ps.expectChar('[');
     ps.expectChar('[');
 
     ps.skipInlineWS();
 
-    const symb = this.getSymbol(ps);
+    this.getSymbol(ps);
 
     ps.skipInlineWS();
 
     ps.expectChar(']');
     ps.expectChar(']');
 
-    return new AST.Section(symb, comment);
+    ps.skipInlineWS();
+    ps.next();
   }
 
   getMessage(ps, comment) {
diff --git a/fluent-syntax/src/serializer.js b/fluent-syntax/src/serializer.js
index b2c2a0583..3b4eb215f 100644
--- a/fluent-syntax/src/serializer.js
+++ b/fluent-syntax/src/serializer.js
@@ -14,6 +14,7 @@ function containNewLine(elems) {
 export default class FluentSerializer {
   constructor({ withJunk = false } = {}) {
     this.withJunk = withJunk;
+    this.hasEntries = false;
   }
 
   serialize(resource) {
@@ -23,11 +24,15 @@ export default class FluentSerializer {
       parts.push(
         `${serializeComment(resource.comment)}\n\n`
       );
+      this.hasEntries = true;
     }
 
     for (const entry of resource.body) {
       if (entry.types !== 'Junk' || this.withJunk) {
         parts.push(this.serializeEntry(entry));
+        if (this.hasEntries === false) {
+          this.hasEntries = true;
+        }
       }
     }
 
@@ -40,10 +45,21 @@ export default class FluentSerializer {
         return serializeMessage(entry);
       case 'Section':
         return serializeSection(entry);
-      case 'Comment': {
-        const comment = serializeComment(entry);
-        return `\n${comment}\n\n`;
-      }
+      case 'Comment':
+        if (this.hasEntries) {
+          return `\n${serializeComment(entry)}\n\n`;
+        }
+        return `${serializeComment(entry)}\n\n`;
+      case 'GroupComment':
+        if (this.hasEntries) {
+          return `\n${serializeGroupComment(entry)}\n\n`;
+        }
+        return `${serializeGroupComment(entry)}\n\n`;
+      case 'ResourceComment':
+        if (this.hasEntries) {
+          return `\n${serializeResourceComment(entry)}\n\n`;
+        }
+        return `${serializeResourceComment(entry)}\n\n`;
       case 'Junk':
         return serializeJunk(entry);
       default :
@@ -55,10 +71,21 @@ export default class FluentSerializer {
 
 function serializeComment(comment) {
   return comment.content.split('\n').map(
-    line => `// ${line}`
+    line => line.length ? `# ${line}` : '#'
+  ).join('\n');
+}
+
+function serializeGroupComment(comment) {
+  return comment.content.split('\n').map(
+    line => line.length ? `## ${line}` : '##'
   ).join('\n');
 }
 
+function serializeResourceComment(comment) {
+  return comment.content.split('\n').map(
+    line => line.length ? `### ${line}` : '###'
+  ).join('\n');
+}
 
 function serializeSection(section) {
   const name = serializeSymbol(section.name);
diff --git a/fluent-syntax/test/fixtures_structure/elements_indent.json b/fluent-syntax/test/fixtures_structure/elements_indent.json
index 266e9a5a0..131459a34 100644
--- a/fluent-syntax/test/fixtures_structure/elements_indent.json
+++ b/fluent-syntax/test/fixtures_structure/elements_indent.json
@@ -161,7 +161,6 @@
       }
     }
   ],
-  "comment": null,
   "span": {
     "type": "Span",
     "start": 0,
diff --git a/fluent-syntax/test/fixtures_structure/message_with_empty_pattern.json b/fluent-syntax/test/fixtures_structure/message_with_empty_pattern.json
index eab2feeae..072d6168d 100644
--- a/fluent-syntax/test/fixtures_structure/message_with_empty_pattern.json
+++ b/fluent-syntax/test/fixtures_structure/message_with_empty_pattern.json
@@ -31,7 +31,6 @@
       }
     }
   ],
-  "comment": null,
   "span": {
     "type": "Span",
     "start": 0,
diff --git a/fluent-syntax/test/fixtures_structure/placeable_at_eol.json b/fluent-syntax/test/fixtures_structure/placeable_at_eol.json
index 83ad25308..6b441ea43 100644
--- a/fluent-syntax/test/fixtures_structure/placeable_at_eol.json
+++ b/fluent-syntax/test/fixtures_structure/placeable_at_eol.json
@@ -203,7 +203,6 @@
       }
     }
   ],
-  "comment": null,
   "span": {
     "type": "Span",
     "start": 0,
diff --git a/fluent-syntax/test/fixtures_structure/resource_comment.json b/fluent-syntax/test/fixtures_structure/resource_comment.json
index a476434ce..3fc128502 100644
--- a/fluent-syntax/test/fixtures_structure/resource_comment.json
+++ b/fluent-syntax/test/fixtures_structure/resource_comment.json
@@ -1,16 +1,17 @@
 {
   "type": "Resource",
-  "body": [],
-  "comment": {
-    "type": "Comment",
-    "annotations": [],
-    "content": "This is a resource wide comment\nIt's multiline",
-    "span": {
-      "type": "Span",
-      "start": 0,
-      "end": 52
+  "body": [
+    {
+      "type": "ResourceComment",
+      "annotations": [],
+      "content": "This is a resource wide comment\nIt's multiline",
+      "span": {
+        "type": "Span",
+        "start": 0,
+        "end": 52
+      }
     }
-  },
+  ],
   "span": {
     "type": "Span",
     "start": 0,
diff --git a/fluent-syntax/test/fixtures_structure/resource_comment_trailing_line.json b/fluent-syntax/test/fixtures_structure/resource_comment_trailing_line.json
index a91e00b5b..dbe67ae09 100644
--- a/fluent-syntax/test/fixtures_structure/resource_comment_trailing_line.json
+++ b/fluent-syntax/test/fixtures_structure/resource_comment_trailing_line.json
@@ -1,16 +1,17 @@
 {
   "type": "Resource",
-  "body": [],
-  "comment": {
-    "type": "Comment",
-    "annotations": [],
-    "content": "This is a comment\nThis comment is multiline\n",
-    "span": {
-      "type": "Span",
-      "start": 0,
-      "end": 52
+  "body": [
+    {
+      "type": "ResourceComment",
+      "annotations": [],
+      "content": "This is a comment\nThis comment is multiline\n",
+      "span": {
+        "type": "Span",
+        "start": 0,
+        "end": 52
+      }
     }
-  },
+  ],
   "span": {
     "type": "Span",
     "start": 0,
diff --git a/fluent-syntax/test/fixtures_structure/section.json b/fluent-syntax/test/fixtures_structure/section.json
index 49b000593..0252e37e2 100644
--- a/fluent-syntax/test/fixtures_structure/section.json
+++ b/fluent-syntax/test/fixtures_structure/section.json
@@ -1,27 +1,6 @@
 {
   "type": "Resource",
-  "body": [
-    {
-      "type": "Section",
-      "annotations": [],
-      "name": {
-        "type": "Symbol",
-        "name": "This is a section",
-        "span": {
-          "type": "Span",
-          "start": 4,
-          "end": 22
-        }
-      },
-      "comment": null,
-      "span": {
-        "type": "Span",
-        "start": 1,
-        "end": 24
-      }
-    }
-  ],
-  "comment": null,
+  "body": [],
   "span": {
     "type": "Span",
     "start": 0,
diff --git a/fluent-syntax/test/fixtures_structure/simple_message.json b/fluent-syntax/test/fixtures_structure/simple_message.json
index 425de818a..5cbe78dde 100644
--- a/fluent-syntax/test/fixtures_structure/simple_message.json
+++ b/fluent-syntax/test/fixtures_structure/simple_message.json
@@ -41,7 +41,6 @@
       }
     }
   ],
-  "comment": null,
   "span": {
     "type": "Span",
     "start": 0,
diff --git a/fluent-syntax/test/fixtures_structure/sparse-messages.json b/fluent-syntax/test/fixtures_structure/sparse-messages.json
index 97882cbd0..d5b57b48b 100644
--- a/fluent-syntax/test/fixtures_structure/sparse-messages.json
+++ b/fluent-syntax/test/fixtures_structure/sparse-messages.json
@@ -337,7 +337,6 @@
       }
     }
   ],
-  "comment": null,
   "span": {
     "type": "Span",
     "start": 0,
diff --git a/fluent-syntax/test/fixtures_structure/standalone_comment.json b/fluent-syntax/test/fixtures_structure/standalone_comment.json
index 2775e6031..3140395fe 100644
--- a/fluent-syntax/test/fixtures_structure/standalone_comment.json
+++ b/fluent-syntax/test/fixtures_structure/standalone_comment.json
@@ -44,6 +44,7 @@
       "type": "Comment",
       "annotations": [],
       "content": "This is a standalone comment",
+      "zeroFourStyle": true,
       "span": {
         "type": "Span",
         "start": 13,
@@ -51,7 +52,6 @@
       }
     }
   ],
-  "comment": null,
   "span": {
     "type": "Span",
     "start": 0,
diff --git a/fluent-syntax/test/serializer_test.js b/fluent-syntax/test/serializer_test.js
index b51f34d71..71b90c752 100644
--- a/fluent-syntax/test/serializer_test.js
+++ b/fluent-syntax/test/serializer_test.js
@@ -76,22 +76,10 @@ suite('Serializer', function() {
     assert.equal(pretty(input), input);
   });
 
-  test('section', function() {
-    const input = ftl`
-      foo = Foo
-
-
-      [[ Section Header ]]
-
-      bar = Bar
-    `;
-    assert.equal(pretty(input), input);
-  });
-
   test('resource comment', function() {
     const input = ftl`
-      // A multiline
-      // resource comment.
+      ### A multiline
+      ### resource comment.
 
       foo = Foo
     `;
@@ -100,21 +88,21 @@ suite('Serializer', function() {
 
   test('message comment', function() {
     const input = ftl`
-      // A multiline
-      // message comment.
+      # A multiline
+      # message comment.
       foo = Foo
     `;
     assert.equal(pretty(input), input);
   });
 
-  test('section comment', function() {
+  test('group comment', function() {
     const input = ftl`
       foo = Foo
 
-
-      // A multiline
-      // section comment.
-      [[ Section Header ]]
+      ## Comment Header
+      ##
+      ## A multiline
+      ## section comment.
 
       bar = Bar
     `;
@@ -125,7 +113,7 @@ suite('Serializer', function() {
     const input = ftl`
       foo = Foo
 
-      // A Standalone Comment
+      # A Standalone Comment
 
       bar = Bar
     `;
diff --git a/fluent/src/parser.js b/fluent/src/parser.js
index bc3efa839..1990ced06 100644
--- a/fluent/src/parser.js
+++ b/fluent/src/parser.js
@@ -72,7 +72,8 @@ class RuntimeParser {
     const ch = this._source[this._index];
 
     // We don't care about comments or sections at runtime
-    if (ch === '/') {
+    if (ch === '/' ||
+      (ch === '#' && [' ', '#'].includes(this._source[this._index + 1]))) {
       this.skipComment();
       return;
     }
@@ -839,7 +840,9 @@ class RuntimeParser {
     let eol = this._source.indexOf('\n', this._index);
 
     while (eol !== -1 &&
-      this._source[eol + 1] === '/' && this._source[eol + 2] === '/') {
+      ((this._source[eol + 1] === '/' && this._source[eol + 2] === '/') ||
+       (this._source[eol + 1] === '#' &&
+         [' ', '#'].includes(this._source[eol + 2])))) {
       this._index = eol + 3;
 
       eol = this._source.indexOf('\n', this._index);