to follow up on what Earl Hood said:
You can't. Messages are written/edited before any other index sorting
is done. To support what you want, mhonarc would have to create sort
lists for all possible sort criteria (an expensive operation), and also
provide a bunch of resource variables to access them.
If the anchor names in the indices were built by rule from the message
ID, you don't have to have sorted the index lists to write the URLs
that index into their HTML representation. You do have to ensure that
every message has an ID, but I think that can be arranged.
I do not see how this solves the problem. Message Ids give absolutely
no indication of listing order, just possible location. It provides no
help in determine what is next, or previous, in date, subject, author,
navigational links provided at the bottom and top of each page). I
do agree that using message ids as indentifiers is better off, in
general, but they provide no assistance to this problem.
You are, of course, absolutely right. I had conveniently reduced
the problem in my mind to "how do I point at my entry in the
Author index." But for that you don't need to change from
serial message numbers as received. Sigh. Sorry.