On the main forum page that show's all of the topics for the forum it shows the name/date of the last user to post in the thread, however I've noticed on multiple occasions that its not accurate.
Here's an example.
It says the last poster was user Flyovergames Aug 6th
However when you go to the last page of the thread:
it shows User: Bilgekaan posted on Jul 24th
So either Flyovergames didn't actually post and its just showing their name randomly, or its not displaying the last post from that user.
I've seen this issue with multiple threads, including getting email "updates" to a subscribed thread, which when you go to that thread, doesn't exist.