>Yet, that's what's happening with the 451 error code. This is clearly aimed at government censorship - what the writer considers the wrong kind.

I'm not sure I agree. While the author may have a certain connotation in mind, "not available for legal reasons" is a simple statement of fact that can be useful for the user, regardless of whether it was a "good" or an "evil" law.

>Unless I'm mistaken, "client" means the browser, not the person operating the browser.

So it shouldn't return a 404? Are you proposing the use of 6xx codes for user error, and keep 4xx for purely client errors? How can the server distinguish between a browser and somebody using telnet? What if another program is performing automated clicks in a browser and navigates to google.com/asdfhjk?

I believe the "client" is "everything on the other end of the tcp connection."

It's very rare for the specs to distinguish between user errors and client errors.

It's also rare for it to distinguish between origin server errors, and gateway server errors.