Your newest proposal is so similar to the original one from the RFC that I
don't see much point in distinguishing it as separate proposal. The
presence or absence of a introducer character is not the sort of thing we
should be debating at this point. As I have said, repeatedly, I have about
the same level of difficulty with the original proposal from the RFC and
the mnemonic proposal, but leaning slightly to the latter.
The point I was trying to make is that I see a substantial difficulty with
your original proposal that simply using the original stuff cures. In
addition, a simple change to the original RFC proposal can provide a
mechanism for alternative representations of the same string using
separate headers. You can get a similar effect by making the substitution
token be the alternative representation, but this only works when the
alternative is something that fits this format. There may well be cases
where a simple substitution token is preferred along with multiple
acceptable string in different character sets and encodings.
Ned