This is a known bug in Firefox 4: [Bug 418975 - Soft hyphen not working in tables][1]. It has meanwhile been fixed, so a future update of Firefox probably resolves this. Some background: To avoid comments to mess up with the layout, [soft hyphens][2] are automatically inserted into comments after 81 characters without whitespace. For me, [that works well][3]: ![Comment with a long code fragment][4] I have the same issue in Firefox 4.0.1 on Mac OS X, both for code fragments and for normal text in comments. No problem in other browsers though. [1]: https://bugzilla.mozilla.org/show_bug.cgi?id=418975 [2]: http://www.fileformat.info/info/unicode/char/ad/index.htm [3]: http://superuser.com/questions/256105/how-to-delete-a-folder-which-is-nested-quite-deep/256130#comment-265284 [4]: https://i.sstatic.net/XuLJu.png