So, I’ve been checking Thesis 2.1.2, bbPress and BuddyPress. It looks to me like it’s all working; no boxes needed.
The important things for forums is that you must have the content displaying on the right archive pages; see my latest tutorial. For BuddyPress you should show have the Post Title displaying because it may show important links (such as Create a Group). I believe all the BuddyPress pages use the Page template… you could create a BuddyPress custom page template, but as far as I can tell so far you would only be able to apply it to some of the pages because the rest are dynamically generated.