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MetaThreads
r/MetaThreads: A place to discuss Threads, the new app from Meta (Instagram/Facebook).
Meta Threads : r/Mastodon
Even if Meta did align its code with ActivityPub, it seems to me that federation with Threads is a decision made on a one-by-one basis by instance owners and I can't see any possible incentive for instance owners to wish to flood their neat and orderly sequence of sensible information-heavy posts with 100 times as much nonsense from Threads.