RE: Header field name case in XML

["Jon Hanna" <jon@xxxxxxx>]

To my mind this is a question about to what extent this format is the same
as RFC2822 and to what extent it is different.

RFC2822 is case-insensitive. This format cannot be. Any attempt to mirror
the cases that are common practice with RFC2822 can only lead to confusion.

There is nothing to stop MessageXML-2-2822 conversion normalising on some
case convention (just like 2822-2-MessageXML conversion MUST). So there is
little real gain from a RFC2822 compatibility perspective in any given case
convention.