FTR the reason I suggested to modify PEP 362 is that we are linking to it from the docs.  This means that people will go and read the PEP looking for clarifications, so the PEP should be clear.  In this regard I see the PEP (or at least the relevant section) as documentation, and given that it's about an aspect of Python that is not going to change any time soon, it makes sense to get it right and keep referencing the PEP.
This doesn't normally apply to most of the other PEPs, especially if what they proposed is now documented on docs.python.org.

(On a side note, I now noticed that the parameter kinds are also documented in http://docs.python.org/dev/library/inspect.html#inspect.Parameter.kind, so we could link to that instead of linking to the PEP.)