Solved: Though the account page refreshed to show and complain about my user name being my email address, I can see that the account name actually did change.

The default user name seems to be my email address. But the site also complains that an ‘@’ isn’t allowed in the name. Okay. But when I try to edit the name the page refreshes back to the old name after hitting the save button. What up?

Hmm, sorry about the inconvenience @neobobkrause. Indeed, at the moment, it’s not possible to change your username, and the error message might have been a cache issue. Glad it’s solved though!