Voting on comments creates some interesting dynamics. Previously, I noticed that there was a comment with a relatively high score, which I was then driven to vote up. This despite the fact that I didn't find the comment itself all that special - somehow, "peer pressure" affected me enough for me to upvote the comment, even though nobody would likely notice.

I'd like to say I cancelled my upvote after realizing this, but I honestly can't remember if I did. I was left torn between the impulse to upvote it and the impulse to correct for the irrationality, and I'm not sure which choice I ended up with. I'd go back and check, but due to the fact that I found the comment itself pretty bland, I have no memory of where it was or what it was about...

On the other hand, after karma became actually meaningful, with the 20-point threshold for posting instated, I suddenly became a lot more careful about whether I'd vote comments up. Previously I'd been doing it pretty loosely, but now I find myself not voting on comments that I previously would have.

Just some more examples of human bias...