re: Diversification, philanthropy, and other things cost Bill Gates $1.2T in wealth

The argument can be made that MSFT would not have the market value is has today if Gates or any other single individual held a 45% stake. There would be a discount due to it being closely held. Bill is probably ok with giving up the stock for the reasons you mentioned such as diversification, philanthropy; and most important, liquidity. I imagine his post IPO life has been exactly the same with a net worth in the billions as it would have been with a net worth in the trillions.