Maybe wasn't that way before, but when signing up on Bluesky now you are asked to choose a instance (bsky.social being the default), and the username contains the instance name, exactly like any Fediverse account.
Maybe wasn't that way before, but when signing up on Bluesky now you are asked to choose a instance (bsky.social being the default), and the username contains the instance name, exactly like any Fediverse account.