It's quite confusing that on https://musicbrainz.org/account/change-password (when logged in, under the user's own header) there's a "Username" field that can be edited. Obviously if someone goes to the change password page when logged in, it should be to change their own password.

I understand the field is there for cases when someone is asked to change the password before they log in (IIRC that was added for our mandatory password reset 10 years ago or so) and it can remain in that case, but it really should be a set hidden field for the default use case.