I think for sure there's a chance that we start to see the same decline in civil engagement as other platforms have seen. Stopping it, or rather not letting it get started in the first place and denigrate a good platform like Medium, is a very tricky proposition in a democracy where people have the right to self-expression.
I think the solution, a term I use loosely, is a combination of factors. First, educate people on how to express oneself in the public sphere. This could and should theoretically begin in grade school, but I'm a grade school teacher myself and I'll tell you, it ain't happening for a number of reasons. No one is teaching logic and rhetoric, for example, and things like debate clubs are not as common in schools. I could go on and on about this (maybe in a future article)!
Second, if people can't argue and reason logically or censor themselves, then it'll have to be done for them. This gets sticky, of course, because who gets to arbitrate this and how? I don't know, except to say we need gatekeepers at places where ideas are exchanged, people willing to say, You're voice is simply not welcome here because you're too hyperbolic, irrational, confrontational...or any of the above.
What if Donald Trump wanted to set up shop on Medium? What a boon it'd be financially for Medium when all his followers came on board and subscribed to read his lunatic rantings. I guess the platform would have to ask itself: the money or our conscience? I vote conscience. But then again, I write for the joy and art of the written word, not to make a buck.