Are you creating your users via regular means or somehow importing them?

Trying to create such user WP prevents me from doing so:


  ERROR: This username is invalid because it uses illegal characters. Please enter a valid username.


The reason for that is that username is validated with validate_username(), which runs sanitize_user() in strict mode. That reduces available characters to basic ASCII set.

In a nutshell WP doesn't consider that a valid username.

So the question is — is that actually a username in your case? Your users might be confusing Username with First/Last name fields, which are not used for login.

If you do want to support usernames like that you will have to override WP validation via hooks. That would probably take some serious testing to make sure it works properly and doesn't introduce security issues.

Wordpress 4 invalid username special charachters issue
In Iron Man 3, Tony Stark has a problem powering the Mark 42 suit.  There is a key scene where he has a panic attack because the young boy says the suit is not charging.  There is also a scene where he is charging it from a car battery.

I've never understood this, as one of the major plot points of Iron Man 2 was Tony developing a new element for the arc reactor which could safety power his Iron Man suit and electromagnet in his chest without killing him.

Tony has the modified reactor in his chest since you can see the triangular shape through his shirt.  So why is it suddenly a problem powering the suit?
