'.' in usernames

[Dean Herington]

The libraries description says about the "User" hierarchy:

> The User hierarchy is reserved for users: a user may always use the
portion of the
> hierarchy which is formed from his/her email address as follows:
>     replace the @ by a ., reverse the order of the components,
capitalise the first letter of each >     component, and prepend User..
For example,
>     simonmar@microsoft.com becomes User.Com.Microsoft.Simonmar.

What if the username itself contains a '.'?  (This is fairly common.)
That could lead to ambiguity.  For example, (perhaps) both
"John.Smith@foo.com" and "John@smith.foo.com" translate to
"User.Com.Foo.Smith.John".

Dean Herington