Well it's not anything written in stone. If you are in a comment chain, everybody's chimin in tryin to add or one up eachother in the sport of it, who can make you laugh louder kinda thing. So every one is involved playin around, why not upvote all. You get points to for upvoting, i think, but yes when you get a troll commment or offensive comment, then yeah, down goes the red arrow. And like Dash says, if people see you upvote, then they will upvote you, maybe even comment and upvote some of your memes because you comment and upvote too.