In addition to what others said, in comments the down vote is meant to be used on comments that don’t further discussion in good faith.

I used to subscribe to that idea, but I’ve since changed my mind. If the far majority use upvotes to mean agreement, then me upvoting a controversial, but well structured, opinion will likely be viewed as agreement as well.

It’s a nice idea to think the voting system is meant to promote discussion, instead of homogenise opinions in a community.