Do Mastodon admins share common blocklists or anything? If a bad actor decided to start posting offensive content to random instances, I assume you can ban that {username | IP} from the instance used by you and your users, but would they then be able to just iterate through the other n Mastodon instances? Is there anything in place to prevent them from creating a new account and repeating ad nauseam? (not that there is on Facebook, necessarily)
(I don't know anything about Mastodon, which I'm sure is obvious from some of my questions - if they're incoherent in the context of Mastodon that's totally fine)
Mastodon instance administrators have the ability to block whole instances, and this is usually done because of bad/nonexistent moderation policies. There is some sharing of instance blocklists, more as a matter of convenience than of policy.
Source: I'm a moderator on a Mastodon instance with about 1000 users (connected to the larger Fediverse of about 2 million users). We've got 5 moderators, and we respond to reports (either by or about our users) promptly and well. We don't have to police the behavior of the whole Fediverse (just our users), and we don't have to protect the whole Fediverse (just our users).