Tom> some people never change the subject line when
  Tom> replying to a digest post.

Including some people who subscribe in digest mode, so
the subject line is just the name of the digest.

However, in about 16 years of subscribing to mail lists
I've seen a nearly infinite number of discussions and
requests regarding list etiquette, and have never yet
seen more than a teeny tiny minority of persons respond
to it.

Complaints about this do nothing more than contribute
to the unwanted off-topic trash on every lists, as do
replies to them such as this one.

I learned a decade ago to stop complaining about the
bad habits of others. What I don't like to see I don't
read. Mail received from lists that looks ugly to my
eyes simply gets deleted without being read.

-- 
Lynn David Newton
Phoenix, AZ