Maybe impose some rules right when they begin creating an account where they can't scam other people and if they do so are banned. Another option is to pay a premium price in which users can comment to avoid scams and see if the user is not trying to scam other people.

Also, a good idea is to sign up in two ways: sign up as a company or as an investor. Companies can only make posts but investors can read their financials without dealing the bots trying to pump the stock/crypto they're promoting.