diff --git a/clang/docs/ClangFormatStyleOptions.rst b/clang/docs/ClangFormatStyleOptions.rst
--- a/clang/docs/ClangFormatStyleOptions.rst
+++ b/clang/docs/ClangFormatStyleOptions.rst
@@ -3795,7 +3795,9 @@
 
 
 **ReflowComments** (``Boolean``) :versionbadge:`clang-format 3.8`
-  If ``true``, clang-format will attempt to re-flow comments.
+  If ``true``, clang-format will attempt to re-flow comments. That is it
+  will touch a comment and *reflow* long comments into new lines, trying to
+  obey the ``ColumnLimit``.
 
   .. code-block:: c++
 
@@ -4610,9 +4612,11 @@
     ///  - Foo                                /// - Foo
     ///    - Bar                              ///   - Bar
 
+  This option has only effect if ``ReflowComments`` is set to ``true``.
+
   Nested configuration flags:
 
-  Control of spaces within a single line comment
+  Control of spaces within a single line comment.
 
   * ``unsigned Minimum`` The minimum number of spaces at the start of the comment.
 
diff --git a/clang/include/clang/Format/Format.h b/clang/include/clang/Format/Format.h
--- a/clang/include/clang/Format/Format.h
+++ b/clang/include/clang/Format/Format.h
@@ -3070,7 +3070,9 @@
   ReferenceAlignmentStyle ReferenceAlignment;
 
   // clang-format off
-  /// If ``true``, clang-format will attempt to re-flow comments.
+  /// If ``true``, clang-format will attempt to re-flow comments. That is it
+  /// will touch a comment and *reflow* long comments into new lines, trying to
+  /// obey the ``ColumnLimit``.
   /// \code
   ///    false:
   ///    // veryVeryVeryVeryVeryVeryVeryVeryVeryVeryVeryLongComment with plenty of information
@@ -3821,7 +3823,7 @@
   /// \version 3.7
   bool SpacesInCStyleCastParentheses;
 
-  /// Control of spaces within a single line comment
+  /// Control of spaces within a single line comment.
   struct SpacesInLineComment {
     /// The minimum number of spaces at the start of the comment.
     unsigned Minimum;
@@ -3858,6 +3860,8 @@
   ///   ///  - Foo                                /// - Foo
   ///   ///    - Bar                              ///   - Bar
   /// \endcode
+  ///
+  /// This option has only effect if ``ReflowComments`` is set to ``true``.
   /// \version 13
   SpacesInLineComment SpacesInLineCommentPrefix;