The Prediction Market Discord Message, by Eva_:

Current market structures can't bill people for the information value that went into the market fairly, can't fairly handle secret information known to only some bidders, pays out most of the subsidy to whoever corrects the naive bidder fastest even though there's no benefit to making it a race, offers almost no profit to people trying to defend the true price from incorrect bidders unless they let the price shift substantially first, can't be effectively used to collate information known by different bidders, can't handle counterfactuals / policy conditionals cleanly, implement EDT instead of LDT, let you play games of tricking other bidders for profit and so require everyone to play trading strategies that are inexploitable even if less beneficial, can't defend against people who are intentionally illegible as to whether they have private information or are manipulating the market for profit elsewhere...

But most of all, prediction markets contain supposedly ideal economic actors who don't really suspect each other of dishonesty betting money against each other even though it's a net-zero trade and the aggreeement theorem says they shouldn't expect to profit from it at all, so clearly this is not the mathematically ideal solution for a group to collate its knowledge and pay itself for the value that knowledge [provides]. Even if you need betting to be able to trust nonsharable information from another party, you shouldn't have people betting in excess of what is needed to prove sincerity out of a belief other people are wrong unless you've actually got other people being wrong even in light of the new actors' information.