[CentOS] Using long usernames with dots in LDAP

Hi,
I have configured openldap on CentOS 4.3, all my users are in ldap.
I also configure idx-smbtools for managing the users.

The test I'm doing is creating long usernames like this:
this.is.avery.long.username

All is working fine:
sendmail, dovecot, idx-smbldap-tools, ceti-poppassd, chown

My question is, I'm breaking some standards? Or breaking some
posix specification by doing this?
It is recomended to have this kind of usernames on Linux?

Many thanks
Oliver

-- 
Oliver Schulze L.
<oliver at samera.com.py>