It happens when people take a dislike to another poster, especially in political forums. Yeah, I've had that happen several times lately. The worst was when I had to wait 128 minutes to comnent. AND you can't even meme comment when you want. When you're the victim of one of these downvote parties, you can just walk away and sait for the next day, or, like I've done, just send a feedback form. Tell them you're the victim of a downvote party and to request a review of the downvoted/ flagged comments. Usually cleared up in an hour or so. One recent feedback got the head of the downvote party put in time out and a lot of the comments he made were removed.
Downvotes are a good indicator of TOS violations, same as flagging. Human review, however, confirms if TOS violations occur.
The key, if you're ever the victim, is to not have degraded to threats or name calling. when mods check the comment threads, they see where the actual abuse is and treat them accordingly.
Caption this Meme 
