(shrug)

My own experience is that positive and negative scores have little if any relation to the quality of a comment.

Also, total signal strength matters. The few massively-negative comments I've seen I agree are bad, but the ones with only a few negatives often don't strike me as deserving their scores.

As most comments don't receive any feedback, positive or negative, having a score of -1 only means that one person cared enough to make the comment and two cared enough to vote it down, for whatever reason.

It would be nice to be able to see total number of positive and negative votes, to see which comments are the most contentious, but that's not currently a feature.