|    The advantage I find in this, is that I'm on 3 primary listservs, and I
|    don't want to sort that mail into different folders, or I'll miss stuff.
|     By having that type of Subj line, it makes my In Box sort into 3
|    categories, so that I can read it by list if I want to.

It depends upon the subscriber's mail client.  Mine, w/o the use of
SUBJECTHDR, allows the placement into folders which automatically
(WINDOW) open.  Unread messages are marked with a bullet.  This is
extremely easy and useful.

Some mail systems do NOT properly REPLY with appropriate SUBJECT: lines
prepending  various :RE:  tokens.

/Pete