This sounds like a strange feature. The last ten posts could be replying to other posts, and won't make sense without the previous ones. Besides, why would you need to only see the last ten posts? I understand it would be less loading time, but just grabbing a few new posts from a thread doesn't seem worth the effort to implement. And, how would this work exactly? Would new posts replying to not new posts be visible, but the original post be not visible?