Raymond,
Regarding COSTs single multivalued RDN which you provided:
You are correct that the encoding violated DER. Does PEM mandate
DER or does it allow BER as a transfer encoding ? If BER is allowed
then PEM implementations must be prepared to perform a BER to DER
transformation in the same way that X.400 applications (for example)
are required to.
But the larger issue is that the single multivalued RDN represents a
misunderstanding of the intent behind naming in X.500. It is possible
to
construct such a beast but it has very limited use and could quite
reasonably be called "wrong".
Note that widespread use of a single multivalued RDN results in a
flat directory tree with all entries residing at the top level.
John