When I read 3720, it is clear to me that the first
processing rule is about comprehending the key.
Declarative vs. negotiated processing rules can only
follow comprehension - if an implementation does not
recognize a key, declarative vs. negotiated handling
is moot. A proposer thus must always be prepared for
the eventuality of lack of comprehension by the other
side, unless the key is defined in 3720 itself.
But I now see that that's clearly not how you read it.
I will add some text along the above lines in the
absence of objections.
