Don't use special characters in a password (for your security...)

The SAI Computing Conference 2016 has a registration page where presenters can register. BTW, one of the tracks is "Security". Registering for the conference will display this error when you try to enter a password with 'special' characters:

"For security reasons..." it is not allowed to use special characters (...). I am not sure if this limitation is recommended by security specialists or even this guy.