The naming of threads seems very strange... I can't see much of a pattern to it at all... "Thread:XYZ 1" could be either a reply to "Thread:XYZ" or a second thread named "XYZ". Also, each post seems to be its own thread, which is rather a strange definition of "thread" (makes sense to the mathematician in me, but for the web user in me, it's very strange).
However, despite that, the implementation seems to work pretty well.