Dan Kohn wrote:
I would say that punycode is compatible with all MIME,
DNS, and Internet application protocols, because it is 7 bits, and so it
transits them unchanged. (In fact, it only uses LDH - letters, digit,
hyphens.)
The latter (use of ldh only), in conjuction with length limits, is
*precisely* what is required for compatibility, as that is what
conventional domain names use. It is not coincidental that
punycode is compatible and is moving forward rapidly through the
standards process and is expected to be widely and quickly
implemented. The same was (and remains) true of MIME; RFC 2047 /
2231 encoding was designed for compatibility (with known gateway
issues and with RFC 822 parsing).