It would be interesting to allow people to link their accounts to Facebook or LinkedIn simply to see if there is any correlation between comment scores and willingness to give up anonymity. If non-anonymous posters routinely score better by a significant margin, maybe you could give a bonus starting point to their comments. Slashdot does something like this with their Karma Bonus system: http://www.slashcode.com/articles/03/01/18/0015227.shtml