The reason why <I> never said anything about it is because it is a documented
restriction, not a bug.  For instance, please see:

* Appendix B of the list owner's or site manager's manual, under
  "Subject-Tag="

* Chapter 6.1.1 of the site manager's manual, under "SET SUBJecthdr"

* Chapter 5.3.6 of the list owner's manual, under "SET SUBJecthdr"

I will admit that this behaviour does not appear to be documented in the
release notes.  However, I would have thought that being documented in
four separate places in the formal documentation would have been sufficient...

Nathan