Seem to have found a small bug, not sure if reproducible but when I was making a reply to a post, I went to preview the post, and then I made some changes, when I clicked preview again, it said it couldn't preview the message because it had no subject. Now, since it was a reply, it couldn't have had a subject.
Anyway, I assumed the post was fine, and submitted it. After going back to the home page, there are two entries for the thread I replied to in the "recent posts" section. I figure this may have been caused by the above bug too.