Rich,
I know, our filtering is a little more aggressive lately for styling and PHP code. We had some issues with spammers and went overboard. We're loosening the restrictions slowly as CSS, PHP, and other things are pretty important to get in this forum.. sorry about that.
The mod you want to make is in the /plugins/content/jfbccontent.php file. Search for "clear". It's the only one in the file. Update that to "clear: left". That should fix that page and be correct for other pages as well. I didn't realize it, but Melissa has already made that change for the upcoming 4.1 release, so it will work that way going forward. If you run into any issues with that though, please let us know. Styling defaults can always be a rough thing, and it's something we're trying not to hard-code as much..
Hope that helps,
Alex