I don't know if this is quite the same thing, but @kersploosh was waging a war on bot accounts. Maybe they have some inside or can come up with something in conjunction with the admins.
Edit: that's @kersploosh@sh.itjust.works in case the one here is someone else.
That's me! Unfortunately, I don't have any clever solutions to active spamming other than responsive moderation, and better mod tools whenever they become available.
I was notifying instance admins of suspicious user totals that looked like swarms of auto-created bot accounts. Last time I checked, half a dozen admins that I contacted have deleted about 250,000 suspicious dormant accounts. It's not a solution to the problem, but it's something.