I don't know if this is possible with the current forum, but it will be useful that the forum system notifies the users when someone replied to their threads or threads in which they have posted, either via e-mail or in PT (like the update notification)
Right now the only way I have to check for replies is to go through the list of my own replies and check each thread for new ones. It's very tedious.
At the very least, it would be nice if, in the "threads started by me" section of my profile, it displayed the user and time of the most recent reply.
In the mean time, for Chrome there is a decent web page change notification plugin that can be used for this. I know there is one for Firefox as well but I forget what it is called.