MIME-Version: as specified in RFC 1341 is admittedly not that harmful.
The April Internet Draft is turning it into a problem. It has to be
handled as a special case when interpreting message/partial. The
modified wording of section 3 means that all sorts of havoc will be
wrecked should the value of MIME-Version: ever change. These
practical matters will likely mean the value of MIME-Version: will
never change, in which case section 3 is recommending implementors
write dead code.
A MIME reader should be able, even encouraged, to ignore MIME-Version:
entirely. To keep from breaking existing software, the next MIME
standard should still require generation of "MIME-Version: 1.0", but
it should mark the header as depreciated and strongly recommend
implementations ignore it. It should also suggest implementors
distinguish MIME messages from pre-MIME message by determining whether
the value of any Content-Type or Content-Transfer-Encoding header can
be parsed using the apropriate MIME BNF.
_.John G. Myers Internet: jgm+(_at_)CMU(_dot_)EDU