Meta just announced that they are trying to integrate Threads with ActivityPub (Mastodon, Lemmy, etc.). We need to defederate them if we want to avoid them pushing their crap into fediverse.
If you’re a server admin, please defederate Meta’s domain “threads.net”
If you don’t run your own server, please ask your server admin to defederate “threads.net”.
You are free to make your own Mastodon/Lemmy instance and federate with them. Being able to block instances is user choice which absolutely IS the point of ActivityPub. There is no one entity that says you must federate or must defederate.