Since this forum can now tell that I have already read all replies in a thread or not, it shouldn't be too difficult to automatically scroll to the first unread post if there are any.
It's not such a large problem yet, but the need to scroll and seek manually is already becoming a bit of a pain in two of the most active threads in this forum (editing vs proofreading & when should a story end).
If you ever introduce multi-page threads, this would be an essential feature.