Actually responding to the thread this time, as a participant...
It's not confusing if the meaning is related. The term "user or
agent" is the actual semantics of this value. I read that as
equivalent to "user agent".
It's not. A user agent is an application that acts on behalf of the
user but is not the user.
UAID is an identifier. In computing contexts such as DKIM, all identifiers
refer to machine-based entities, possibly ones that are representing humans.
The only concern I have here is that because "user agent" has a
specific connotation, there could be confusion about what happens to
it when a user uses more than one UA. Suppose I use Gmail's web
client, Mulberry, Apple Mail, and Thunderbird, all at different times,
and all sending mail as <barryleiba(_at_)computer(_dot_)org> through Gmail's
email infrastructure. (In fact, that *is* the case.) Should the UAID
that Gmail sticks in the signature always be the same, because it's
just me, using these client programs interchangably? Should it be
different for all of them, because they're all different UAs? Should
the webmail version use one UAID, and the others use another, because
there are only two submission mechanisms involved (web vs SMTP to port
I can see that someone implementing or configuring a system wouldn't
be sure how to set this up, and at least part of the confusion would
be due to interpretation of "user agent".
I also agree that we should spend too long on this point... again,
speaking as a participant.
NOTE WELL: This list operates according to