I have a multi-site installation of wordpress currently running, and I am having some problems with user registration.
Currently, I use an external authentication plugin (similar to LDAP i guess) and I use this to validate usernames/passwords. For this to work, every user is first added to the Wordpress list of users, and the plugin checks against this list.
The problem is that my organization allows periods inside of a persons username (eg, john.smith). Wordpress is not allowing me to enter john.smith as a username into the system (only allows a-z characters).
Is there any type of workaround for this? I would rather not edit the wordpress core as thats a horrible practice