Edit: Ah, incorrect. He actually intended it to be a chapter-by-chapter deconstruction but never completed it.
Because if that's it, then it was just two points he was making, 1. Null-terminated char arrays are "defective"/unsafe, and 2. Don't omit curly braces, for which he seems to have received a lot of backlash, even though those are quite valid points. I'm guessing it may have something to do with taking it up against the grandfathers of C and his rather ...hands-on writing style?
Critique 1. isn't actually that controversial, and does have merit[1], and 2. is a stylistic decision, that even John Carmack[2] would agree on.
[1]: https://news.ycombinator.com/item?id=20792938
[2]: See "Spacing" in https://kotaku.com/the-exceptional-beauty-of-doom-3s-source-...