Last Call question about encoding of <mailbox> in popimap-downgrade

Hi.

This is another "are we sure?" question.    I'm happy if the
answer is "yes" or "makes no difference", but am obligated to
ask.

The current text of Section 4.1.7 of popimap-downgrade-06
requires that any <mailbox> that contains and <addr-spec> that
contains non-ASCII characters be rewritten into a Group with
encoded words.  In the spirit of the rest of popimap-downgrade,
that is certainly the right thing to do if the <addr-spec> has
non-ASCII characters in the local-part, e.g.,
    non-ASCII <at> ASCII-FQDN
or
    non-ASCII <at> non-ASCII-FQDN

but, suppose the <addr-spec> were 
    ASCII-local-part <at> non-ASCII-FQDN

A clever downgrader could rewrite the non-ASCII-FQDN into
A-labels if needed and thereby avoid the Group stuff and
preserve a deliverable address.

Do we want to explicitly allow that option?  My personal guess
is that any IMAP or POP server implementation that decides to go
to the trouble of this downgrading model will figure out that
possibility and ignore us if we do not, but I could be wrong.

best,
   john