Or maybe they could just remove Downvote button for everyone and let users upvote content they like and if it's something really bad (not just different opinion) then there is Flag button and if you flag something there should be displayed "Flagged by XY for reason: XY" you would need to fill and which could be seen right under flagged comment.

But I knwo this is never going to happen because it's too transparent and welcoming diverse opinions and you could suddenly see all those anonymous internet heroes.