Subscription= By Owner,Confirm was never available (and similarly, neither
has "Closed,Confirm"--but I think that would be fairly obvious:).  The 1.8c
documentation is however ambiguous.  My beta-1.8d master copy says under
Confirm=, however:

***

    Open:            The users are allowed to subscribe to the list.
    Open,Confirm:    Before the users are allowed to subscribe to the list
                     they must confirm their address with an "OK" response.
                     No list owner intervention is required.
    By owner:        The users are not allowed to subscribe, but their
                     requests will be forwarded to the list owner. This is
                     the default.
    Closed:          The users are not allowed to subscribe, and their requests
                     are not to be forwarded to the list owner.

(The ",Confirm" option is used in conjunction with "Subscription= Open" only.
It has no effect with the other two levels.)

***

So the ambiguity has been cleared up in the beta manuals.  I wish I knew
when I did this, though; I can't find a revision note for it :(

Nathan