Phillip Hallam-Baker wrote:
RECOMMENDED is a strong suggestion that the implementation may override at
the discretion of the implementer. SHOULD is normative.
So the first tells me that I can make up my own mind, the second says that
I should give a reason if I don't comply.
This is only half of the story.
PKIX (rfc5280) defines the concept of a "minimum requirements RP",
i.e. an implementation which implements only MUSTs, and potentially not
a single SHOULD. Essentially, this waters down all SHOULDs to MAYs.
-Martin