It does, for the most part! Defederation is the last resort, when you've got an instance that nobody wants to deal with (e.g. the people there are tracking down

It does, for the most part! Defederation is the last resort, when you've got an instance that nobody wants to deal with (e.g. the people there are tracking down and harassing your users, and you want them to “win” and therefore stop). User-level moderation tools are much more common, though they're currently a bit lacking.