The score most certainly not even. HTTP is still way, way behind. There's a qualitative difference between a spelling error in the document describing the protocol and a spelling error in the protocol itself. In my opinion, the substantive point wasn't about the mechanics of referrers, but that the lack of care and attention to detail demonstrated by "Referer" is strong evidence that HTTP is not as elegant as you claim.
I worked a bit for a small newspaper in Amsterdam in the 1980's, called 'the paper about Holland'. It was written by two UK journalists, Abi Daruvalla and Mark Fuller.
We were pretty good at proofreading because spell checkers were non-existent at the time, we barely had a word processor. It would probably surprise you that as a non-native English speaker I would catch typos (not grammar errors) much quicker than the rest of the (native speakers/writers) crew. We figured it was because they didn't actually read the words where I had to. They'd mentally fill in the word that should have been there which allowed them to proofread a piece with three individuals and I'd still catch the mistakes in the spelling.
In spite of that we managed to ship two issues labeled September in one year, and that's with everybody being so focused on the spelling that nobody bothered to check the dates.
I think you're reading way too much in a single letter spelling error (which I spotted the first time I saw the word), the common excuse is that the spell checker used by the person that wrote that part did not include a spelling for 'referrer' (and if it had it would have probably ignored it with the leading capital anyway...).
I've seen some pretty elegant code with terrible spelling errors in the variable names, it's certainly not great to have a spelling error in a text protocol. But I would not use that single letter mistake as a yardstick by which to measure the entire protocol, that seems all too easy a way to discard something that has stood the test of time very well.
