James Gasik
We don't talk about Pun-Pun
This is something of an interesting topic, as Gary both warns against changing the system in the introduction on page 8-Can you provide a page number for this?
But then in the afterword on page 230 says-
From what I've been given to understand, Gary knew that DM's would alter the rules to suit their games. But at the same time, was wary of people riding on his coattails and creating their own variant games, as well as wanting to make a clear distinction from D&D and AD&D for business purposes. Hence the "Such campaigns become so strange as to be no longer AD&D".
That he himself didn't use all the rules in the PHB and DMG is well-documented, as Gary was an inveterate tinkerer- it's hypocritical for him to say that nobody else should do the same! But at the same time, he wanted everyone to play according to his "vision", like human-centric worlds, no monster characters, and being exceptionally harsh to those dirty, dirty players!