I would like to see a tagging system that could be used for filtering or just viewed on the comment itself. I almost always view every discussion board I'm on as wide open as possible in order to see taboo-breaking or uncomfortable opinions and to get an idea of where the population of readers is leaning on a topic and tags by other users would also be useful. It's more information about why people like or dislike things, which I find almost as interesting as the comments themselves.