BuddyPress.org

By default, you are allowed to use a limited set of HTML tags like [img]and [a]. What type of tags are you wanting to use but can’t?

You could write a small plugin to either remove these restricting filters or expand the whitelist of allowed tags, but you have to have trust in your group admins!

I’m using the former in the following example (put this snippet in your theme’s functions.php):
http://pastebin.com/CWryrkDT

Like I said, only do this if you trust your user base!