And that's fine, but chances are that any instances which would federate with Threads would probably get defederated by many of the instances which refuse to federate with it. We've already seen this behaviour in fediblock drama, where merely being able to see content from "bad" instances is enough to get your own blocked by an entire union of censorious Mastodon admins.
If I'm on instance A and my friend is on instance B and she is talking to someone on Threads (instance C) and instance A blocks instance C .. it just means I won't see posts from instance C. So maybe my friend on instance B gets into a conversation with someone on instance C. In my view I just don't see the C side of the convo. No harm, no foul.
A lot of the fediblock stuff is not 'well they won't defederate from the BADPEOPLE so i'll defederate from them too!'. In fact I'm not sure I've seen an example of that actually happening. You often see grousing and calls for it, but I'm not sure I've ever seen it happen. Most of the block lists i've seen are simply instances of 'free speech warriors' who refuse to moderate calls for violence from their userbase, instances that are straight up 'we are nazis' here, or instances that are extremely sketchy porn.
