At the moment there is no way to hide a users username from other users. This is especially a problem in case of anonymous access. Any user can access the instance and view the username of the other users. This exposes one of the credentials needed to login - username. After that, one only needs to determine the password.

There are a few methods to hide the username from the UI, but it is still available in the HTML source of the page.

This is needed for security reasons.