do i remember correctly that masto federation looks up accounts by acct instead of by the numerical id
@aescling it is theoretically possible to fix this dependency on acct, but it is a lot of work AND it still wouldn't allow username switching if you're interested in compatibility with upstream mastodon
the best way to enable username switching would be by adding an additional property which represents the used username while maintaining the old immutable username for webfinger access, account URL/IRI, and mastodon compatibility
or by adding pseuds, which likewise
@aescling mastodon happens to use usernames in its URIs (okay look technically they’re called IRIs) but even if it didn't it wouldn't matter because it does webfinger by acct so that is its single source of truth