The scale in which the downvoting system affects conversation can be quite aggravating in some cases. I wonder why Riot decided to model this after Reddit's Board style instead of one that is more traditional. I don't like seeing a joke post being made and that being the top of the comments section, while actual conversation is... right at the bottom. It's not too helpful.
However in the case you're describing OP players may be a little up in arms about the balance of champions they like. Again, I noticed that with your most recent thread the biggest conversation happens to be one that isn't anything like the topic. Everyone knows Riven has a low winrate right now, right? There's individual threads about that and everything. That shouldn't punish your thread views.
Ignore my rambling. Hey, I like that you're making threads that encourage a little bit of discussion though. I suggest avoiding commenting on everyone that doesn't contribute. Don't reward (or give attention to) stupid or you'll see more of it.