Nathan.. I'm confused.. you wrote:

> You can't.  Archiving is an all-or-nothing venture; it's either on
> or off for all messages sent to the list.

but Pete indicated you could:

main-list:  * topics= HTML, NOTEBOOK= NO
sub-list:  * NOTEBOOK=YES,..

List-owner thens Subscribe sub-list to main-list; then  SET main-list
TOPIC: ALL,-HTML FOR sub-list

Posters use:

SUBJECT: HTML: yady-yady-yawn

QED

 ........Cleo  [log in to unmask]