In some email I received from Perry E. Metzger, sie wrote:
> 
> Darren Reed <darrenr@reed.wattle.id.au> writes:
> > Whilst looking through the PR's currently open, I came across one where
> > a person was attempting to chown a file to a user where the username was
> > made up of a ".".  Easy to deal with ?  Maybe.
> > 
> > Consider that a username might be "foo.bar", "foo", "bar" and a group
> > name to match each of those.
> > 
> > If I do "chown foo.bar /tmp/foryou" what should happen ?
> > 
> > Is the best option, in this case, to simply bail out because the user
> > is not being clear about what they want to do ?
> 
> There are two possibilities here. The current docs we have don't even
> indicate that "." still works. In theory, we could perhaps just rip it
> out.
[...]
> Or, of course, we could just rip it out.

There are already #ifdef's in chown.c to disable use of '.' as a user/group
seperator.

Darren