I've rarely seen instances get blocked on large Mastodon servers for no reason at all. I've seen plenty of small ActivityPub server projects struggle to federat

I've rarely seen instances get blocked on large Mastodon servers for no reason at all. I've seen plenty of small ActivityPub server projects struggle to federate with Mastodon, though. Unfortunately, very few AP servers are spec-compliant. It does make sense to defederate single-user instances instead of individually banning their account, though, because you can simply reject messages rather than processing them and then applying moderation status to the underlying account.