[Setup] plone usernames starting with digits

[Steven McDonald]

Hello

    It  seems that I can not create a usename that starts with a digit. 
Is there a reason for this? Can it be configured otherwise? We have a 
group that would like to create a user called 8pi, it is a name they 
have used on many other accounts and would like to keep it for their 
plone site for consistency.

Thanks
Steve McDonald