FWD: Confidential Request for Help (Do Not Forward)
As it turns out, the email in question was sent to the list owner by a non-list-member, with the idea that the membership of the list could help with the specifics of the request. So the forwarding by the list owner to that list was okay; however, any further forwarding was to be strongly discouraged.
Still, seeing this in the inbox gave me quite the "WTF?" feeling.