Corgana

If they choose to migrate to another instance, it will likely be a more extremist instance with poor moderation that has been significantly defederated.

In theory this is how it should work, but in practice the toxic people tend to move to general purpose more laissez-faire places like .world or .ml, which makes de-federating and cutting off 30% of all users a difficult decision for anyone trying to have a community.

The answer is less centralization, but that can’t be forced. beehaw.org (for example) made the decision to cut off .world and they are better for it. But they are a large-ish instance in their own right.