I still don't think anyone here should feel good about paying attention to current total while deciding whether to upvote or downvote. Share evidence, not conclusions. The net karma a comment ends up at should be the result of aggregating our valuations, not a result of, say, whether those who thought it should be at +100 voted before or after those who thought it should be at +2.
Edit: it's clear to me now that I don't have a good solution to my perceived problem.
It seems to me that your suggested policy would result in comment-placement effects being even stronger than they are now. What score should a comment end up with if 50 people consider voting on it and they all think it should have a score of +2?
From this 2001 article:
I, at least, found this amusing.