I'd really like "I learned something" as a vote button. It's poisonous to think that I agreeing with something means I have to adopt the other person's stance on an issue, and if I disagree I have to denounce their contribution as horrible and bad.

Some of the best stuff I've ever read didn't change my overall stance on the issue, but gave it nuance and depth it didn't have before, and more respect for the person on the other side.