This is a critical feature missing.
Especially considering when one instance goes down, so does your account.
If announced, we should be able to easily transfer the account.
But an instance might also go down unannounced (especially now with so many hosting instances just for fun or to experiment with it).
While in such a case your posts and comments on this local instance will be gone, there needs to be a way to recover your account on another instance with all your posts and comments made on other instances still connected to your account, being editable or deletable.
For robustness against disappearance we kinda need multi-account linking. You set up accounts on a few trustworthy to be resilient instances and link them.
At the moment you are completely dependent on the instance [operator]. Which could disappear for a multitude of reasons.
The average user will be confused enough as it is about the federated aspects. They may choose any random instance to register. And suddenly it's gone.
You have to create a new account on a new server then use the account migration tool. It’s not perfect; you’ll keep your followers but I think your posts won’t transfer over. Notes from the tool:
Before proceeding, please read these notes carefully:
This action will move all followers from the current account to the new account
Your current account’s profile will be updated with a redirect notice and be excluded from searches
No other data will be moved automatically
The new account must first be configured to back-reference this one
After moving there is a waiting period during which you will not be able to move again
Your current account will not be fully usable afterwards. However, you will have access to data export as well as re-activation.