diff -r 70f55dc9d43f Lib/idlelib/FormatParagraph.py
--- a/Lib/idlelib/FormatParagraph.py	Wed Jul 10 17:02:24 2013 -0400
+++ b/Lib/idlelib/FormatParagraph.py	Thu Jul 11 13:57:11 2013 -0400
@@ -38,7 +38,7 @@
         first, last = self.editwin.get_selection_indices()
         if first and last:
             data = text.get(first, last)
-            comment_header = ''
+            comment_header = get_comment_header(data)
         else:
             first, last, comment_header, data = \
                     find_paragraph(text, text.index("insert"))