There is a reasonably well-known example of a large forum that charges users for account creation.

Something Awful has charged $10 for account creation for as long as i can remember.

While I do think it has kept away most low-effort trolls, there have certainly been deeply toxic attitudes and arguments still happened. Doxxing, organized harassment, racism and similar nastiness have certainly been issues with some regularity in most of the subforums.

The only reason why it has been kept down is a relatively large team of admins and moderators, and they have been far from infallible, there has been tons of drama in that regard, including at least one mod who literally doxxed other forums users to white supremacists.

On the whole though, the discussions there are a lot more civilized than on sites like Reddit. I think the small entry fee is part of it, but also thanks to an active moderation team and the standard policy being to put people in timeout first, instead of insta-banning for any offence.

Obviously there are differing views on how well it actually works, leading to various spin-off forums, with different policies and philosophies.

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.

No.

Here’s a thought experiment I’ve come up with to illustrate this: what happens tomorrow if we shut down all social media (to whatever level you define social media.)

This gets to the crux of the issue - the underlying reality of the speed of information broadcast/transmission and the social-informational structures that are constructed to absorb it.

We probably already have the means to develop tech to solve this, its just not in the interests of most SM platforms - and since they're proprietary you can't really make a 3rd party company to offer a filtering / "lens" solution either.

Metafilter did this, and I think was highly successful in terms of maintaining civility, but it’s no less an echo chamber.