In the first generation of MMORPGs, the pyramids were skinny and tall. In the current generation, while I think the peak should still stay way up there, the slopes projecting down from it should be less extreme. What I want to make is a theme park where both casuals and hard-cores can exist and play together. That’s the minimum requirement I think a modern MMORPG should fulfill.
For the most part I agreed with the latest letter, but this particular paragraph didn't make sense to me. I can see what Yoshi-P is saying in that he wants the casuals/hard-cores to play together, but making the difference between hard-core players and casuals less extreme ruins exactly what hard-core players play for.

By lowering the difference between casual and hard-core players, you ultimately cheapen any accomplishments one might make in the game. So called "hard core" players are only hard core when the reward is proportional to the work they put out. If you make the rewards less potent, you'll soon find your hard core players disappearing due to lack of reward (and any MMO knows, it's the hard core players that keep the games going).

Think back to FF6. People fought for hours to uncurse that cursed shield and get the paladin shield. It was worth the work and it was one item out of many that clearly set you apart from a casual player. If it were only marginally better than any other shield everyone would have laughed and said no thanks, beat the game, and then moved on to other things.