First of all, I think making changes is a bit premature -- nobody AFAIK
is complaining about the current stream of requests.  That said, Mailman
has the ability to create "virtual" mailing lists called topics:

https://www.gnu.org/software/mailman/mailman-member/node29.html

It would be straightforward -- once we agree on any topic names -- for
Seth/Chris to implement topic filtering.

Aahz speaks for me on this.  I don't find the current level any problem at all, and a sub-list tag
wouldn't be a problem either.

-- Alan