My issue with this is that, quite aside from my lack of understanding of what's going on, the author is constantly professing their lack of understanding of the underlying details.

> I still don't know a thing about what F or Coyoneda mean. But it isn't really slowing me down.

They're essentially cargo-culting signatures, and while sometimes that can be enough to stimulate proper understanding, I worry that the first time something goes wrong the author will be hard-pressed to solve it. It seems like a useful way to stumble around in unexplored areas; it doesn't seem like a good way to build software you're going to have to maintain and support.