>
> Do you want the subscribers to opt-in or -out of the "discussion" topics?
>
> The way you have proposed, they will have to out-out.
>

Current subscribers will have to opt-out by filling out a form. New subscribers opt-in
to either the newsletter only or the discussion plus newsletter. Both group receive
ads.

> Messages sent with NO topic or an incorrect topic are treated as the
> reserved topic OTHER:
>

I think this answers my question. I can QUIET SET subscribers who want the discussions
(as well as newsletter and ads) to OTHER, NEWS, and ADV. For subscribers that want
only the newsletter, I can QUIET SET them to NEWS and ADV only. This last group would
then NOT receive any "discussions" (i.e., messages with No topic, which fall into the
OTHER topic area).