Ah, maybe I misunderstand what you're trying to do. I thought Hal was trying to make it possible to write clients that can buy from Amazon or eBay without knowing anything about the specifics of either. But actually what it's attempting is a sort of machine-assisted documentation system? (Since you still need a human to read the docs to find out how to signup, place orders, and so on.) I can see how that might work, but it doesn't seem like an important problem to solve.
That is one of the benefits that relates to documentation, which is the part of your comment I was responding too.
The larger goal of hal+json is to establish some conventions for linking that allow the development of generic tools for doing hypermedia. Not to create magical machine clients that can interact with any random API you point them at. Nobody made that argument so I don't know why DHH addressed it in his post. I'm guessing he ran out of things to be an angry-pragmatist about.
Well ... the spec does say "HAL is a bit like HTML for machines, in that it is generic and designed to drive many different types of application." To me (and perhaps DHH), that suggests that it's designed to be used to create clever clients. Perhaps you can clarify this point in a future edition of the draft?
I have no idea why you would conclude that from that sentence. HTML allows browsers, the same way that HAL allows generic libraries. I'm struggling to understand why this is controversial, there are already 16+ examples of generic HAL libraries across a bunch of different languages.