Interesting observation about social media in a book I'm reading. It was a dead end with for-profit platforms, but Nostr could be different?
How can we introduce expensive signals? Maybe allow people to put up a bond in sats for x years that gets burned if it turns out they spread incorrect information? Since nobody is in charge, users could appoint a number of npubs that can make the slash happen? 
IMO the only way to accomplish this is to require a fee for every post. Different platforms might have different fees. If Lyn Alden is posting alpha, perhaps she would pay .0001 bitcoin with the expectation that she would receive more than that in value back. If we’re just shooting GMs and GNs around the horn then it would cost less but the quality of content would go down.
Ultimately we’re fighting that information is “free” from a marginal cost of production. So if we’re worried about the good information being lost in the clutter of the other information, then we need a financial “proof-of-work” to post. It would probably include a subscription model of daily expense to consume as well.
Who decides if information is correct?
(There's a secondary question, is there an ethical basis for punishing someone that spreads information that is adjudicated to be false, without knowing for sure that they knew it was false when they spread it; if yes, then how can anyone know that for sure?)
I've probably said it before, but I was absolutely shocked when I heard "serious" people starting to use the term fake news some ~15 years ago. The world is full of lying of course, and half truths even on highly respected media, but the idea that "fake news" is a real thing that needs to be legislated sounded, and still sounds incredibly childish (see above). I still genuinely don't get it.
The real problem is not the spreading of falsehoods, it's the cancer of stifling free speech because people are saying things you disagree with, with threats of violence - which actually *creates* much more spreading of falsehoods via backchannels. I saw this first hand in China.
(None of this means I disagree with applying the handicap principle to stuff like online discourse, that's an interesting topic but it won't solve "fake news", because that is a broken concept).
As I said "nobody is in charge", by which I also mean that nobody gets to decide what is correct.
But you could opt-in to have other people hold you to a high standard of intellectual honesty. That could include not spreading information that you knew at the time was unreliable, but would get lots of zaps.
It's still up to yourself or your group of peers to figure out what standards to hold and how to enforce them. The latter is a really hard problem if your goal is to avoid group-think.
Voluntary-basis fact checking is interesting, but honestly I don't see it actually working except in edge cases.
It indeed remains to be seen. Perhaps one day someone figures it out.
I do think the incentive now is too much such that the silent majority can't stop nonsense (in their eyes) from spreading. Unless you speak up, the default is for the spreader to receive likes, sats and reposts from the subset who agrees.
To some extend that happens in a bar too in that people will avoid confrontation. But there's a bit more signal in the form of blank stares. Maybe fact checking isn't the right way to address this though.
I've been slowly listening to this:
https://www.youtube.com/watch?v=FQlA-I7PXf0&t=5408
And taking notes. It reflects this idea you are referring to
