There is one (new?) problem in Section 3.2:
(The SMTP MAIL FROM address should be available in
the Return-path: header field if sieve processing occurs after
final delivery.)
That's not the case for bounces.
I must be missing something here. A bounce message normally has an empty
MAIL FROM. This means that the return-path would also be empty, or not
provided, or whatever, and the lack of this information should be sufficient
to say "don't sent a vacation notice".
A bunch software writers thinks
different and as a result, the local part mailer-daemon at larger sites
is flooded with vacation responses of various systems real bad. I know
that the Sieve vacation extension tries to avoid that by not responding to
well known addresses, but that does not make the above statement correct.
I suggest to remove references to "Return-path:".
Mailer-daemon normally appears in the From: header, not in the MAIL FROM
or return-path.