I wonder if you could do that kind of thing on a large scale. Require a small contribution, say $1 a year, and use the proceeds to hire a moderation team that was deliberately coached to allow controversial arguments but prevent malicious echo chambers from poisoning the entire ecosystem.
It would necessarily be a less profitable site than the competition, but that might not be a problem as long as it wasn't venture-funded.
There's one way to promote healthy discussion. Instead of just up and downvoting, you can give people the option to vote for "well argued" and "I agree" separately. I've seen a Finnish newspaper site use this.
It would necessarily be a less profitable site than the competition, but that might not be a problem as long as it wasn't venture-funded.