I was glancing through the mod log and saw these two entries. Conspiracy theory communities were both removed for violating rule #3.
What are these rules? If I look in the side bar, rule #3 on both lemmy.ml and sh.itjust.works to me looks like no porn. So why were conspiracy theory communities not allowed? That seems like kind of a community that shouldn't be an issue on Lemmy... are conspiracy theory subs really something that won't be allowed here? Honestly that's kind of disturbing to see already...
Your terminology is super confused, but the lemmy.world admins did remove those specific communities on lemmy.world in particular. They're unaffected on other servers, and other communities from these servers continue to replicate to lemmy.world unimpacted.
I knew users can block specific communities from their feeds, but I figured the admin level was just defederating from the instance as a whole, like beehaw did.
I don't run an instance and don't have a lot of experience with exactly what's possible, but the screenshots in this post pretty clearly show community removal and not defederation... and the communities aren't removed on their home servers. So I infer the lemmy.world admins must have been able to do it... and did so.