Different people want to see, and want to avoid seeing, different things. The net karma score of any given comment is an expression of our collective preferences, filtered extremely noisily through which subset of the site happens to read any given comment.

I would prefer LW not try to impose voting standards beyond "upvote what you want, downvote what you don't want." If we want a less croudsourced value judgment, we can pay someone we trust to go through and rate all the comments, though I would not contribute to that project.