Using non standard characters in usernames

Hi firstly apologies if this post is in the wrong section.  I am interested in opinions / views on allowing

members to use "non standard" ($,!,@) characters in there nickname.  Any experiences / problems encountered ( security ?) feedback appreciated

I have a mod that accepts spaces in NickName, I think it should be ok accepting special characters as well also you might need to URLENCODE the NickName.

Regards,

Jomar -- dolphinbugfixing.com