A bit of lore that I learned in my networking class in college was that the RFC name was chosen as tongue in cheek in that by the time a proposal gets to the RFC stage, comments are very much not appreciated. You're supposed to comment well before that point.

No idea if that bit of lore is true but it is certainly the case that RFCs are usually the final word on the relevant standard. In fact, once they get their ID, RFCs cannot be modified or rescinded; only superseded by another RFC.

Finally I understand why RFCs are served with the Do-Not-Comment header!

Then they should be renamed CFCs (closed for comments).