In other words, your post may still be visible on, say, a linked Mastodon server, even if you decide to delete it with Threads.

“I think this is a downside of the protocol that we use today, but I think it’s important to let people know that if you post something and another server grabs a copy, we can’t necessarily enforce it,” Cottle says.

… it’s not a downside of the protocol, it’s just a literal impossibility. Once someone’s downloaded something, you can’t do a thing to take it back.