On Thu, Sep 20, 2018 at 05:00 PM, Brian Vogel wrote:

Or even a line that reads:   This message was sent by <fill in from address
here>

The problem is, as you've noted, that there is no easy way for a plain-text
message recipient to "go private" with the originator of any given message, at
least in the e-mail interface. 

Hold on, this is getting confusing (I read digest..).
Unless your group allows anonymous posts, I don't see the problem. On properly configurated listserves, my email-program will show who the sender was, and give me the choice to reply to the group or to the sender. If on digest, I will just have to copy-and-paste the private email-address and edit out the irrelevant pieces of quote.
Only on yahoogroups (and this is a rather recent thing) I have to scroll all the way to the bottom of the individual message to see who the sender was (which is annoying, especially if (s)he doesn't trim).

groetjes, Ronaldo

Ronaldo,

            If you read what others have said, you'll get why the need is there.   It is a grand PITA, particularly if you can't see, to attempt to extract the originating member's e-mail address from the headers on the message.

            I can do that with ease, but others can't.

--

Brian - Windows 10 Home, 64-Bit, Version 1803, Build 17134 
     Explanations exist; they have existed for all time; there is always a well-known solution to every human problem — neat, plausible, and wrong.

          ~ H.L. Mencken, AKA The Sage of Baltimore