I agree with your general point that the Federalist Papers aren't quite the same as a random blog post. But to extend that analogy further, if I'm implementing HTTP, should I base my implementation on things only found in a blog post by Tim Berners Lee?

Don't get me wrong, the Federalist Papers are important historical documents and provide unique insight into the minds of the authors. But they're not laws, and treating them as if they have actual legal significance seems wrong.