Where do you see a difference? Like you said, there is a libertarian argument that can be made for why insider trading is desirable. If the bet is easily manipulable, like how many times someone will visit a place, then the rational response is for others not to bet on that market. The same argument still holds.

You can disagree with the libertarian argument, but I don't see how you can say that Polymarket et al. are something other than a prediction market. Can you explain where you see the difference?

It’s not a libertarian argument for prediction markets that they should have insider trading, it’s the point of the exercise. The way they work is to incentivize people with knowledge to externalize the knowledge to the market. The concept of fairness doesn’t even make sense in that context.

So if a market is trying to maintain a veneer of fairness it’s just using a prediction market as cover and is something else.

I'm not a libertarian. My basic policy take on these "markets" is that they should be outlawed.