I've been wanting something similar to the text format buttons in use on most forums (such as this one) that allow commenters who have no knowledge of HTML to add bold text, italics, linked text etc in their comments.

I've just added a script on my weblog which I developed from UBB code that seems to work well (MT3.2), so I'm making it available if you want to try it out.

The current version supports URL link formatting, bold text, italics, underline, strike and blockquotes. The URL linking in particular resolves the issue with wrapping on your comment listing page when visitors want to post a really long URL.

Download the script and instructions here (zip file):
http://demon.twinflame.org/mtscripts.php (buttons included)

See the script in action on the comments form here:
Urban Scrawl (please don't spam the sh*t out of me testing it tho - just use the preview button to see your results, thanks).

I'm not offering support for it - it's an 'as is, where is' script, but it's pretty basic so you shouldn't have any problems. Tested in Firefox1.0.6 and IE6.0 and validates as XHTML 1.0 Transitional for those who are concerned about that sort of thing.

cheers.