[CentOS] Why are dots in username & groupname no longer allowed?

On 1/5/06, Johnny Hughes <mailing-lists at hughesjr.com> wrote:
> BUT, the I think that the real reason that dots should not be allowed in
> user names is because this doesn't allow dots:
>
> RFC 4282 - The Network Access Identifier
>
> There is no requirement to follow this for usernames; however, I think
> we should.

Unless I'm misreading the RFC, it does allow dots in usernames?

   nai         =  username
   nai         =/ "@" realm
   nai         =/ username "@" realm

   username    =  dot-string
   dot-string  =  string
   dot-string  =/ dot-string "." string

Josh Kelley