In section 6.6, rewriting the From header is suggested as a way to
signal inconsistencies -- such as the ones that could be expected
when messages are forwarded through a mailing list -- to user
agents.
According to section 5.2.2, signing the From header is mandatory.
Hence, if the advice from section 6.6. was applied, DKIM signatures
would be invalidated. User agents would no longer be able to verify
the binding between the signing address (if different from the From
address) and the message.
Regards,
--
Thomas Roessler, W3C <tlr(_at_)w3(_dot_)org>