Besides that, I think the stylistic changes this author is commenting on are fairly minor. I think the conciseness of vertical space was a bit confusing sometimes; this article only shows the simple functions where it works. The almost complete absence of templated is more likely because no STL code was used.
Certainly, the code base is very thorough. When I realized I had to use quaternions to represent the player's orientation in the game space, there was already an idQuat class ready and waiting and fully functional, which was very nice. I think that idQuat class was never even used anywhere in the base code, so it was cool -- for someone with who never knew about quaternions before then -- to have a class fully implemented and ready for me to use.