There’s definitely better ways to handle this, like, the ID could be a public key or something. Chances of RSA/EC key conflicts is basically nonexistent or we wouldn’t use them.

But it’s the W3C, of course they assume URLs can and will be permanent. Your domain being seized is not something typical companies and organizations face. It’s something you expect to happen to a site hosting piracy and other illegal content, which FMHY is somewhat borderline with its piracy guides.

ActivityPub is not designed to be any sort of censorship resistant for sites that move addresses and servers frequently.