Advertisers are probably paying more content farms to astroturf it though.

Yup, in fact we just banned ~13 accounts tonight from a subreddit I'm still involved with. That's just the ones we identified, and it's only a medium sized subreddit

A user noticed that the responses to a post sounded a little off and reported it. Turns out there was a network of bots using generative AI to mix real academic advice (ex. "Go talk to the advising office") with occasional subtle advertisements (ex. "I recommend using grammarly and (advertised service)".

Once we caught on, we looked through the history of those accounts and gathered as many as we could identify and banned them all.

I don't think this is Reddit's doing, and they're usually good about banning spam bots site wide once a mod report is made. Still, they benefit from increased activity and they have an incentive to do less of that. It was also much harder to notice the problem because of the AI generation. If a user didn't explicitly report it, I probably wouldn't have noticed