Beehaw.org, a large powerful Lemmy server, has defederated from Lemmy.world and sh.itjust.works in response to a severe harassment campaign involving porn-spam and death threats.
This means beehaw.org users and communities are now cut off from Lemmy.world and vice versa.
The full details are a bit hard to follow, but the TL;DR: Beehaw.org wants a curated community and Lemmy.world doesn't. Beehaw.org has a tougher sign up process while it's basically free at Lemmy.world.
But that's not a big deal or the real drama. People are all looking into the future. /R/piracy has moved into the Fediverse, as have pornographic servers. So now there are discussions on all sorts of topics and what should be or shouldn't be federated.
That's fine. The federization model works, but differently than what Redditors are used to. So I think people are confused about how things play out on the Lemmy-community.