Currently, participants and moderators need to scan through each idea thread to see if any new comments have been made on that thread.  Many discussion boards have the ability to show you what is new since your last visit and take you right to that new post.

This functionality would make it easier for participants to keep up with the flow of the dialogue, could help threads from being buried, and would make it easier to moderate.  Additionally, it might encourage more people to register to participate to gain this functionality and bring them closer to posting or rating.