NickName – allow more chars (space, non latin)

Is it possible to allow more characters in fields builder -> NickName without causing problems?

I know how to modify the check. I want to kow if it's safe – if someone runs a site without having issues.

Anything other than what's currently allowed has the chance to break something. Spaces are known to break the JavaScript, as does ' and similar characters. You're better off using the first and last name fields, and setting them to display instead of the username (Administration -> Settings -> Advanced Settings).

Thanks