I vote for quality as well as agreement. If a comment makes sense and is explained well, but I don't agree with it, I'm still very eager to vote it up. I also

I vote for quality as well as agreement. If a comment makes sense and is explained well, but I don't agree with it, I'm still very eager to vote it up. I also doesn't make sense to comment along the same lines of another commenter. If my opinion is already expressed in the comments, an upvote makes way more sense imo.