Random thought: the interesting thing about voting systems where 'disagreement' can align with a downvote: your most interesting comments should be highly upvoted AND downvoted, ultimately hovering around 1.
It means half the people agree, and half disagree, bringing about the most discussion. And, isn't that the point of comments?
I don't expect a particularly strong correlation between "good comment" and "half of people agree". Nor do I think those are going to bring the most discussion. And most discussion is not the point of comments either.
And all those caveats are just for a purely agreement-based voting system. When you add in votes based on quality, comments hovering around 1 are usually iffy.
It means half the people agree, and half disagree, bringing about the most discussion. And, isn't that the point of comments?