I don't understand the problem. If you want your mail from this list
to have a subject that looks like:

[LSTOWN-L] Subject-Tag

all you have to do is send mail to

[log in to unmask]

or to

[log in to unmask]

(depending on which one you're subscribed on)

with the command:

SET LSTOWN-L SUBJ

The list does not need anything special done to it. Subject-tag= is
only if you need to use a tag different than the list name. And no
one is forcing anyone to use the subject-headers. Anyone who wants it
can SET it, and those who don't, don't have to.It's all up to
each subscriber's individual preferences -- what's worth discussing?

Puzzled,

Francoise