The term "signer address" is mentioned several times in the draft.
Section 6.6 contains the following:
In order to retain the current semantics and visibility of the From
header field, verifying mail agents SHOULD take steps to ensure
that the signing address is prominently visible to the user if it
is different from the From address. If MUA implementations that
highlight the signed address are not available, this MAY be done
by the validating MTA or MDA by rewriting the From address in a
manner which remains compliant with [RFC2822]
Maybe I'm up too late, but I cannot find anywhere in the draft
where the signer address is actually presented within the email
message.
It appears the i= tag of DKIM-Signature is the closest thing, but
it is optional.
--ewh