It might be interesting to have some form of statistics about C9 activity. Many communities have a vast silent majority and a vocal minority. Maybe the "casual, drive by" poster has been reading the forum for a while and got sick of useless junk posted constantly by some.
By statistics, I mean initiated threads and replies, on the one hand, and threads read/last login/login count/login frequency on the other hand. The star system might be a good way of ranking individual posts, but it's also highly subjective (I don't read every single post around here and I certainly won't rank each).
Besides, there's the risk of people replying indefinitely just to increase their activity stats, and there's one last question: Beside your ego being hurt by some "drive by" poster's opinion, what would the final purpose be?