Non ASCII chars get mangled when a new user is created.
Sample name: äöüß becomes äöüß (ok, this is extreme for usernames, but at
least full names must be enabled to have non ASCII characters).

It is one of the common problems when running an application server on Windows:
the default charset of the server is cp1252, the charset of the web application
is UTF-8. When you don't take care of this, you'll get in trouble.

There is a puzzling effect: After you edit the name as an administrator, the non
ASCII chars are correctly displayed!

Another effect is, that the user list becomes longer and longer whith entries like:
äöüß
äöüß
äöüß