It's currently available.. But you have to request the admin to change the username

manually changing the username will break federation due to the assumptions that current implementations make. proper username changing support is something we'd like to do, but we'd have to address the elephant in the room...

Before (strangely) switching to using the federated username for all user-facing but internal systems such as the profile URI, my account's URI used to be https://mastodon.social/accounts/106986373252061228.

Using this system – which Instagram, Twitter, and Facebook do – would at least alleviate this problem internally.

However, as #4053 (comment) states, federation is impacted.

Although perhaps this would break federation, that is something that I am comfortable with if the user is duly notified of before the operation commences.

Despite all of those crude methods achieving explicitly what I desire, Federation remains ultimately problematic in this regard.

Consequently, all of this may be unnecessary, because Mastodon has a system of redirection that should remediate all of these concerns:

1. If desired, the date of the old account is transferred to a new account (which the user has previously created in Mastodon's unnecessarily manual implementation).
2. Subsequently, the old username (federated, and to an extent internally) redirects to the new username. Consequently, the renaming process is in fact superior to the aforementioned social media accounts’.

https://ems.element.io/tools/matrix-migration and https://mastodon.social/@beedellrokejulianlockhart#:~:text=has%20indicated%20that%20their%20new%20account%20is%20now%3A demonstrate this ability well.

yeah it would be nice if the account URIs actually didn't depend on username, because that's kind of the biggest issue -- see #51 (which i regret partially because i didn't know enough at the time to argue clearly) and also #51 (comment) (by which point i was better at articulating the issue)

for what it's worth, pretty much every single big implementation makes the same mistake in putting the username into their id. mastodon only ever uses those numeric ids for its API and nothing else. operations internally are done on acct which comes from webfinger. activitypub id is not used for anything other than the activitypub serializers and delivery worker.

technically we could do something like this for a one-time migration

• generate new actor documents at routes that depend on snowflake/hash/etc user ids instead of on usernames
• set alsoKnownAs appropriately
• generate a Move activity from /users/username to /users/userid` and deliver to all followers (or maybe all known servers?)

but this would be really expensive and all old posts would be orphaned (since there's no Move handler for posts, only for accounts)

at the very least: we could start assigning new users independent ids. and if you have a "legacy" account that doesn't support username changes, you will have to make a new account and migrate to it if you want to be able to change your username later.