I think one problem is that there are two different ways people can vote. One is to cast a vote for or against a comment, expressing your opinion. This works well when there the point total is low.
The other way is to vote towards how many points you think is should have. So if something has 15 points, if I agree with it but think it's not that good to have 15 points, I sometimes downvote it. Likewise, I'll upvote some heavily downvoted comments because they weren't that bad. I figure no comment should be below -1 unless it's overtly belligerent or trollish.
I've thought the same thing. But, I think that to say that a comment has X number of upvotes so it's good or bad doesn't really work since there's no max points a comment can have, or knowledge of how many people voted on it, I'm sure there are some other variables that would make it work.
My idea to solve the problem you're talking about is to have 3 ways to vote. The usual up/down (which in this case can be agree/disagree) and a third for good comments that the user doesn't particularly agree with. It's a rough idea, but I think it could help solve the problem.
Something else I've been toying with that's along similar lines involves removing any up/down/other voting and instead uses a small area of say, 50x50 pixels. The X axis would be the quality of the comment, the the Y would be personal agreement with the comment. And the user could just click anywhere within that area to express their opinion. It's not as easily quantifiable as regular voting, but allows for more expression.
This is a good idea. I've certainly seen great comments (that I may have disagreed with) at some negative score, and terrible comments with scores of like 23.
A "I think this is a good comment" or "I think this is a poor comment" is certainly different from "I agree with this" or "I disagree with this". The later seems to be how the voting system ends up degenerating into sadly.
The other way is to vote towards how many points you think is should have. So if something has 15 points, if I agree with it but think it's not that good to have 15 points, I sometimes downvote it. Likewise, I'll upvote some heavily downvoted comments because they weren't that bad. I figure no comment should be below -1 unless it's overtly belligerent or trollish.