That's a good question. I don't know. My guess is that you could be exposed to Threads content you don't want in the same way you could be exposed to Mastodon content you don't want. I can't imagine they're not set up to respect blocks, mutes, or server suspensions though, right? They have a way bigger problem than Threads if they don't.

What do you mean discovery feeds? Like the federated/all tab?

Because those feeds only show posts that the instance knows about, which is (mostly) posts from people that at least one person on your instance followed.

If you check the all tab on a small instance, it's a lot quieter than it is on something like mastodon.social.