Here's an idea.
I had a discussion up earlier that touched on toxicity as well. But after thinking about it, I have a possible way of dealing with it.
Why not just let it be like it is on like, Xbox or PlayStation? Have no chat restrictions. And I know at first y'all are gonna think, "That's the stupidest thing I've ever heard."
Hear me out.
At least when you play, say, Call of Duty or Halo, you can defend yourself verbally, right? Well in League, you can't. If you do, you are punished in the same way that the instigator would be.
So that's why I'm saying that the chat restrictions should be done away with. If your team doesn't want to listen (read) the two of you (or however many) fighting, they can just mute the lot of you and go on with playing.
As far as AFK/intentionally feeding players, that's another issue that I don't think anyone will ever be able to solve without ruining the game in another way.