I actually love the upvote/downvote mechanism here. An upvote takes the place of a low-content positive affirmation like "good explanation" or "I agree," which

I actually love the upvote/downvote mechanism here. An upvote takes the place of a low-content positive affirmation like "good explanation" or "I agree," which helpfully increases the content:filler ratio for other comment readers. A downvote takes the place of tiresome rebuttals to tedious arguments. If somebody posts "vaccines do cause autism" in a discussion about health care costs, I can just downvote and move on. Without downvotes, people are tempted to make the diversion worse by posting retorts ranging from "go away, troll" to several paragraphs of carefully cited rebuttal. Or if everyone manages to refrain from Feeding the Troll, then the bad comment appears to be just as worthy as every other comment that wasn't rebutted. From what I've seen of relatives who get sucked into lengthy arguments on Facebook, they can't break away because there is no downvote, and letting bad arguments sit otherwise-unchallenged looks like a (weak) endorsement from other participants.