format_paragraph_event():  Patch 961387 introduced a bug here, causing
the indentation of a comment block to be ignored when reformatting the
block, leading to overly long reformatted lines (too wide by an amount
equal to the indentation width).  Looks like a typo in the original
patch, a 1-character repair.
diff --git a/Lib/idlelib/FormatParagraph.py b/Lib/idlelib/FormatParagraph.py
index 80c654e..ed9f28d 100644
--- a/Lib/idlelib/FormatParagraph.py
+++ b/Lib/idlelib/FormatParagraph.py
@@ -47,7 +47,7 @@
             lines = map(lambda st, l=len(comment_header): st[l:], lines)
             data = "\n".join(lines)
             # Reformat to maxformatwidth chars or a 20 char width, whichever is greater.
-            format_width = max(maxformatwidth, len(comment_header), 20)
+            format_width = max(maxformatwidth - len(comment_header), 20)
             newdata = reformat_paragraph(data, format_width)
             # re-split and re-insert the comment header.
             newdata = newdata.split("\n")