The dig at Kernel is kind of depressing. It's probably an evolutionary dead end, but god damn it, the world is better when people try things. Dismissing them doesn't make you cool.
I don't see any comments on Kernel in the post. I didn't waste my time reading the book, but the post criticizes unhygiene F-expr, which is known to be awful and is exactly what Kernel aims to solve and supersede (via hygiene F-expr).
“Functions use dynamic scoping. This is categorically a mistake, and one which ironically has been suggested to seriously mess up fexprs.” (links to Kernel)
It’s possible my interpretation wasn’t correct and the author was citing Kernel’s approach as sanity. That would make sense technically.