How often do you upvote comments like that? Those comments you disagree with, yet are well-thought-out, add a lot to the discussion or at least your understanding of what's going on and other people's points of view.
I don't think people do that enough and it leads to comment-bloat. "I'll make my point and then add in a platitude to draw in the upvotes, hopefully balancing out the downvotes I'll get for my opinion."
I'm probably slightly biased toward upvoting comments that I agree with, assuming similar good quality, but I tend to upvote comments I disagree with fairly often as well.
I don't think people do that enough and it leads to comment-bloat. "I'll make my point and then add in a platitude to draw in the upvotes, hopefully balancing out the downvotes I'll get for my opinion."