I suspect that there's going to need to be some analysis software that can run on the kbin and lemmy server logs looking for suspicious stuff.
Say, for instance, a ton of accounts come from one IP. That's not a guarantee that they're malicious -- like, could be some institution that NATs connections or something. But it's probably worth at least looking at, and if someone signed up 50 accounts from a single IP, that's probably at least worth red-flagging to see if they're actually acting like a normal account. Especially if the email provider is identical (i.e. they're all from one domain).
Might also want to have some kind of clearinghouse for sharing information among instance admins about abuse cases.
One other point:
I would recommend pre-emptively banning as many bot accounts as possible,
A bot is not intrinsically a bad thing. For example, I was suggesting yesterday that it would be neat if there was a bot running that posted equivalent nitter.net links in response to comments providing twitter.com links, for people who want to use those. There were a number of legitimately-helpful bots that ran on Reddit -- I personally got a kick out of the haiku bot, that mentioned to a user when their comment was a haiku -- and legitimately-helpful bots that run on IRC.
Though perhaps it would be a good idea to either adopt a convention ("bots must end in "Bot") or have some other way for bots to disclose that they are bots and provide contact information for a human, in case they malfunction and start causing problems.
But if someone is signing up hordes of them, then, yeah, that's probably not a good actor. Shouldn't need a ton of accounts for any legit reason.
