I think this is a meaningful security problem. Most users won't know that the domain name matters. They'll learn eventually, but lots of opportunity for mischief in the medium term.

If you have `n1c.bsky` and then migrate to `n1c.dev`, Bluesky should set `n1c.bsky` as a redirect to your destination domain by default. If you ever choose to terminate that redirect, `n1c.bsky` can go back in rotation... but it should have an immutable record that you registered the name originally, migrated to `n1c.dev`, maintained a redirect, and released the redirect on <DATE>.