Mark Lloyd writes:
Don't ignore the difference between a usenet POST and a usenet THREAD.
That is important. When reading a post in a thread, the reader has
ALREDAY been exposed to the quoted material, the response (at whatever
location in that post) is read AFTER that other stuff.

Not necessarily true. Usenet does not guarantee delivery
of postings so a reader may be coming into the middle of
a thread. Also, people don't always continuously subscribe
to newsgroups so they may have missed earlier postings.
You may have read all the postings in a thread but that
doesn't mean everyone else has.