It seems to me that some of the things we're discussing are outside the
realm of MIME, and that we should refocus on precisely what we're trying to
In particular, MIME can transport text and voice messages.
With text, the purpose (as I understand it) of the various headers is to
convey to the user agent the information necessary to choose the correct
character set and language conventions for displaying the message.
Language variants that have no impact on the textual display, I believe,
therefore do not need to be represented in the MIME headers for text
delivery. I believe that simplifies the problem, at least incrementally.
For voice messages carried by MIME, I believe that language specification
has no effect on the message delivery and is therefore relevant only to the
recipient(s) of a message, in giving them a clue of what to expect. I
personally suspect that this function is largely unnecessary, as a message
sender is likely to tailor a voice message to the language(s) understood by
the recipient(s). I especially suspect that detailed dialect header
information is unnecessary for this purpose.
Am I missing the point?