Maybe we could deprecate the practice of not including an explicit hash
specifier in clearsigned messages. This would then only be done by
pre-OpenPGP versions. OpenPGP versions would always include an explicit
hash algorithm.
Then since the deprecated practice only occurs on pre openpgp versions
we could say to assume md5 in that case, for backwards compatibility,
similar to what we do with symmetrically encrypted packets. This sends
the message that we don't want to prolong the misery of md5 while still
making it work with the old PGP messages out there.
Hal