Does anyone have a requirement for characters that are not supported by
PrintableString? I do not want to add complexity unless it solves a
problem for someone.
Well, given that PrintableString doesn't include "@", anything that might
include an RFC822 email address needs something else.
The big picture is that anything that is in a human language should use UTF-8.
We don't need it for RFC822 email addresses, domain names, or URLs, since they
are all defined as ASCII. Similarly, dates can be specified at UTCTimes.
However, policies, warnings, contracts, and so on that might be embodied in an
attribute MUST be able to be written in UTF-8 so that non-US folks can
unambiguously state what it is they are saying.
--Paul Hoffman, Director
--Internet Mail Consortium