The Article says that HTML is a derivative of XML. IIRC, HTML comes from SGML not from XML. And SGML is definitely made with being written directly by a human in mind.
True, perhaps a better description would be that HTML is a sibling to XML.
Whether HTML was intended for humans or not, it isn't in my opinion a particularly nice way to develop applications. Don't get me wrong, I love web applications, but writing them with HTML isn't a requirement.
I agree that writing them in HTML isn't a requirement, but saying that as being a sibling of XML and not being made for humans to write is not a good argument against writing it.
Btw, Gaffa sounds like a nice idea, definitely interested on how it plays out in the future.