So, the instance I joined Lemmy on last week largely to participate here defederated from lemmy.world an hour ago. It’s early post-Reddit days, which is the only reason I’m posting a general tech tip in /r/!austin, but it’s a previously impossible inconvenience that isn’t theoretical. Choose wisely or start your collection of alts early!
IMO, defederation should be a last resort when all else fails, reserved only for the most toxic of communities in which modding efforts have either failed or become too much for volunteers to handle.
Honestly, I think a “quarantine” function could be a nice feature to have in the future, where an instance could designate other instances (such as lemmynsfw) as opt-in federations rather than defederating them outright. May give users a bit more agency and control over the content they see without having it all be up to each server admin.