It's there when you look a the overview of the forums. But that only shows the last 10 posts. When you go in to one of the forums, the list of topics only shows the number of posts and the date/time of the last post. Unless you can remember how many posts were there last time you looked, or the date and time of the last post, the only way to see if there is a new post is to open the topic and scroll to the bottom.