What does that mean in basic terms, can someone from a mastodon instance see everything in threads.net without a login to threads.net?
Posts are not just going got flood over, though. Each Mastodon instance has its own local view into the fediverse, and discoverability depends on what other users on your instance have subscribed to. Some instance admins will decide to not host anything Meta, or limit discoverability, as they do with other servers.
https://www.theverge.com/2023/12/13/24000120/threads-meta-ac...