There are some comments which I wouldn't normally upvote or downvote, but if I think they've been upvoted or downvoted disproportionately to their value, I'll try and redress the balance. For example, if someone asks a banal but well-meaning question and it gets downvoted, I'll upvote it.

I consider this marginal rather than flat-out inappropriate, but I've upvoted posts to avoid paying a karma penalty for replying to them. Someone I've discussed this with withdraws the upvote (click on the boldface thumb to withdraw a karma point) after having commented.

I've mostly tried to avoid upvoting so far, and I've completely avoided downvoting.

My model for upvoting right now is:

• If I've commented on a post, I should upvote it, because if it was good enough to comment on, then it was good enough to upvote.

• If a post or comment is particularly well thought-out, well-reasoned, or otherwise showing an understandable mastery of the issue at hand, it's worth considering upvoting it.

• Don't upvote unless I'm absolutely confident, because I don't want to go skewing the statistics here, and I'm also pretty new at this.

My model for downvoting has been:

• Don't do it until you know why other people do it (hence this post).

I've also been trying to understand why posts get comments and up/downvotes, but the two don't seem to correlate well. So are there different rules for upvoting comments versus posts?

I down vote posts I think are bad for the sites reputation / public image. I think people who like controversy or trolling privately benefit from such posts and externalize reputation all harms onto the site overall. I also think people in general benefit from a forum with good members and don't factor in long term reputational effects. I use karma to help people internalize these better.