The RFC is far more useful in dealing with the word "should". It is used in the standards to mean something that is optional but strongly recommended ("there may exist valid reasons in particular circumstances to ignore a particular item"), whereas in english the first definition that comes up is "used to indicate obligation, duty, or correctness".
To me it seems that there could easily be confusion between these two interpretations.
To me it seems that there could easily be confusion between these two interpretations.