Do keep in mind though that diamond can also be earned pretty easily through playing games with stays (hopping properties, etc.), not to mention the $40k CC spend route. I am gold but could be diamond already for next year if I had been interested in gaming the stays.

I would be all for a true high-roller tier to compete with SPG and Hyatt, based only on nights (no funny business with stays) and including big perks like super late checkout, confirmed suites, etc.

I know you post about this on a rather frequent basis based on a couple of anecdotes, but I very strongly suspect that this doesn't really happen very often. I can tell you I sure haven't been taking any diamonds' upgrades from them because I can count on one hand the number of times I've ever been upgraded to anything of significance as a gold (which is fine - I really care less about the room aside from being in a quiet location. The only perk I really care about is free food...).

I would imagine that if and when it does happen, there are other factors at play - time of check-in, room type booked in advance, need for 1 vs 2 beds, etc. etc. It should not ever be the case that if two people, one gold and one diamond, walk up to the desk at the same time with the same prebooked room type that the gold is upgraded and the diamond isn't. And I sort of doubt that that happens much. If it does, then I think that it speaks more loudly to the ambiguities and inconsistent application of the hhonors program that is pervasive across the entire system than to anything else, which is why I'll keep beating that drum of brand standardization and clarification of benefits.