Trojan account? Win some level of trust then share affiliated links or product later as if from a legit trusted member of the community? This is more complex social engineering potentially, but it’s fairly obvious when they put little effort into intervening posts before the affiliate link or product promotion comes …
I’m not sure how you’d automate catching that.
One part of the solution: I don’t let low trust levels post external links. TL2 on one of my forums. That means the poster has to put quite a lot of effort in before they can post what they really wanted to post all along. (Because of this I’ve seen recent accounts sometimes suggest what people should put into google search to find what they are promoting! lol). Once they drop that payload they miraculously disappear and never post again.
I believe I caught someone reviewing themselves from another account. When I checked the location of the IP it was the same as the business service provider that was being reviewed. What are the chances given the business was an online business with customers all over the world? Catching that is also not something that would be easy to automate?