Why YSK: Beehaw defederated from Lemmy.World and Sh.itjust.works effectively shadowbanning anyone from those instances. You will not be able to interact with their users or posts.
Edit: A lot of people are asking why Beehaw did this. I want to keep this post informational and not color it with my personal opinion. I am adding a link to the Beehaw announcement if you are interested in reading it, you can form your own views. https://beehaw.org/post/567170
But can C see A through B?
My understanding is that Lemmy isn’t peer-to-peer, it’s more like hub-and-spoke, relative to the instance that the community is on.
So if users on B and C are interacting with a post on A, then it’s the responsibility of A to be the postman and handle the syncing between A<>B and A<>C; B and C don’t directly talk in this case.
Thus, nobody outside of Lemmyworld sees posts from Lemmyworld made on Beehaw communities, because Beehaw doesn’t accept them, and therefore doesn’t pass them along to the other instances, either.