Had a client the other day complained that he could not update his username on the panel, then i realised he was talking about when you go to
Applications > WordPress App > Users > (click on user account)
The username field seems to be a text-input field, every time you type something in there, you even get a little " ✔️ Saved" notification, but it does not work.
[Small Bug] Didn't think it's worth a support ticket.
