mastodon meta, "moving" accounts
I just read "Notes to Self on Mastodon" from @jimniels and see the common wish for "moving" content between Mastodon instances.
That's one of the trade-offs of this particular protocol. You can copy the address book, but you can't (easily) change history.
You said what you said, when & where you said it. When you said it, it was replicated to thousands of servers. It might live at a particular URL on your local instance, but it also lives in many remote databases.
To properly "move" would require updating every instance to which you've ever sent a message. Otherwise, no one knows where your stuff went. References and reply threads would all be broken.
We sort of get this for edits and deletes on individual fediverse messages. But, doing this for the entire history of an actor would be fraught & onerous.
It would be like expecting that if you moved from Yahoo Mail to GMail, all the messages you've ever sent get an updated "From:" header in all the remote inboxes and mailing lists to which you've ever sent a message.
Instances could maybe accept imports of content, if only as archived history. But, this would likely be unsatisfying for most other purposes.