It would be great if users can vote on comments. Like stackoverflow.com: Vote for answers to push them to the top of the list or just answer "Was this post helpful to you?" with yes/no.
I'd be 90% more likely to actually vote on an idea if the links from the IdeaJam Activity Summary actually logged me into the site. If I have to go and dig out my login details, most of the time I just don't bother.