It makes quite a lot of sense to me that if an IMAP server
supports a specific charset in some other context (such as
IMAP SEARCH and friends), it should be consistent about
supporting the same charset in UTF8 too.
Inconsistency here would be unreasonable for the user - and by
pointing to that, we have "reduced to a previously unsolved
problem".
Suggested language:
If the server supports other charsets in IMAP SEARCH or IMAP
CONVERT (add references to taste), it SHOULD also support
those charsets in this conversion.
