Dave, 1 year ago

Servers are independent. You can only create the same username if it's not already taken. dave@gmail.com and dave@hotmail.com are the same username but different servers. You don't get dave@gmail.com reserved just because you have dave@hotmail.com, but if it's available you can register both.

Is there a way to have that account scrape whatever data you want to back up, saved posts etc from your ‘ghost account’ or your original account on the other server?

Lemmy is pretty young and there aren't a lot of tools. Most likely in future there will be an ability to transfer you account to another server, notifying other instances of the change. But this would require the home server to be available for approving the transfer otherwise you would have people stealing other people's accounts.

Mastodon (a twitter-like federated site) has an option to migrate an account, but as I understand it, that's more about moving your followers to your new account. I don't think the posts move. This page claims there it's a technical reason so perhaps we wouldn't have that on Lemmy either - but Mastodon does re-direct accounts, so perhaps on Lemmy in the future your posts might still point to the old user but if someone clicks on it then it will take them to your new account.

None of this is sorted yet so ideas will probably change over time.