All in all, it doesn't mean much. Mastodon makes the domain part of your ID, so moving to another server isn't different than, say, moving to Twitter. Even if it's possible to move your existing content, it doesn't have significant value on an ephemeral timeline. You might as well save your backups and keep going.

Mastodon might be able to force your followers to follow your new account, but AFAIK it doesn't do that either for reasons I don't know. That would've been cool.