The encoded word has the encoding as one of its 3 required parts. If
you want to use the encoded word to explicitly identify a 7 bit
character set, say iso-2022-jp, with the current specification you
This brings up a question, Eric, is the "q" encoding excessively
burdensome for none ascii text? I confess that I have not studied the
2022-jp specification yet, but if the set of octets is passable as
ascii they would generally not require quoting. The incremental
Let me try a different answer and hope that Erik will come up with a
similar one. ISO-2022-JP involves passing ESC characters as part of
the switching sequence. Robustness argues very strongly for quoting
those somehow, since some defensive UAs (and occasionally MTAs) strip
them in the hope of avoiding logic bombs in messages. They are also not
"printable" in the usual case.
This might suggest that, if one needs a "7" quoting designation, then
one might want either something 2022-shift-specific or a 7 bit
designation that provides for quoting controls but not graphics.