Not good!
Edit: he does link to it in the post. But if you read his post then read the CFAR "Eat Dirt" chapter it'll leave you unsettled.
The third paragraph has a footnote stating that the 3 para above were "heavily inspired" by the "Eat Dirt" chapter. I'm assuming you didn't see this first footnote.
And a bit later, I do link to the manual as well (which is what you saw, I guess)
Not my intention to copy Duncan's work. A big red disclaimer hurts readability, and not attributing the source would indeed be plagiarism. I think I struck the right balance.
I use that example because I love how it shows the concept I was trying to explain pretty well. It's not the main point of the post.