I have another question:

If a thread is obviously filled with low effort responses, many of which are plagiarized, then I think it would be safe to assume that much of this spam is done for promotional purposes. Those are obviously against the rules, as incentivized posting in a specific thread is not allowed.

Are mods checking for when spam in a thread would become to much to lock it or delete it? Or would it help to also crowdsource that kind of reporting?

Right now I see most of the  accounts reported here banned, often in the same day... Which is good. But what about those that actually paid for the spamming? The OPs of the thread and the projects being promoted? Why should the rest of the thread remain up if it is generating so many pages of spam in a day.