I did a little testing, and think I answered my own question.
If the list is Send= Editor,Hold then you get two Approved-By headers.
If the list is Send= Editor (not Hold), then you get just one.
 
I guess it has to do with the fact that a Hold message can't be changed
by the Editor so you can assume that the authour would approve of it,
whereas the message of a nohold list can be changed by the Editor
and no such assumption about the original author's approval can be made.
 
Right, Eric? If so, very nice subtlety --typical of what I would expect
from LISTSERV.
Peter
 
>Date:         Thu, 9 May 1996 21:27:44 PDT
>From: Peter Rauch <[log in to unmask]>
 
>Why are messages that are sent to an edited list (Send= Editor,hold)
>posted, after approval by the Editor, with TWO APPROVED-BY: headers?
 
>The first Approved-By: header contains the list Editor; the second
>Approved-By: contains the original author's address.
 
>(Does it have something to do with the fact that the message was "Hold"?)