such action would be a direct violation of the section of the RFC I quoted. The "robot" is not the author; its mailbox does not appear in the header field intended for the mailbox of the author. The "robot" is also not the agent that introduced the message for transmission, it is retransmitting a message already in the system.
If I had a secretary and I instructed him to forward messages related to certain topics to designated recipients, he would be the author of the new messages that contain the original messages. The section I quoted allows this. How is this different from having a list server perform the same task?
A multi-post digest is reasonably consided a new message. One that is "authored" by the list server. With the list owner as the responsible agent. As best I can decern, the people at IETF do not think this is a violation. So, why not a digest with just one post?
I think you and I are viewing this from two different perspectives. You seem to view the list server as part of the mail transport and delivery infrastructure. I view the list server as an "electronic secretary" interacting with, but outside of the mail infrastructure.
Granted, proper use of Resent-From and Resent-Sender would be the best solution. How likely do you think it would be for all the Sender Authentication systems to be updated to use these fields? I think very unlikely. So, that leaves it to the list server admins (and, possibly, developers) to implement a work around.