Although I am a fan of the LISP school of program design (minimal global state, build small functions and macros, make sure they work, and than build more functions and macros on top of that, until you have an abstraction that you can build your app on), Carmack raises some interesting points: If you're handling a lot of global, mutable state, you may want to abstract minimally, so that you can see where that state is mutating, which makes bugs easier to spot.
Maybe the key idea is to put all the global state mutations as closely together as possible, so they can be compared and contrasted as easily as possible.
Not a bad idea.