Originally Posted by
nikolastojsin
Thank you, that is greatly appreciated, and answers my question - my reservation was through Amex FHR; it never made much sense that reservation paid at the hotel would not earn points, but that is what they insisted HH policy was. (To quote them directly, "It is the reservation that counts; if you reserve at a third-party site, the rate is ineligible.")
Ah well, thankfully, competition in US lodging is quite plentiful.

(As opposed to airlines, for example.

) I still find it silly that HH would risk losing a 60-80 nights/year client over things like these, but...
Since you're not booking with them, they feel they shouldn't care much about you. Your loyalty was really with the credit card company on this booking, not the hotel!
When it comes to loyalty - it works both ways. Hilton pays out fees and commissions to others when you book thru 3rd party sites, such as American Express. They determined since they've already paid out those commissions, they're not going to pay out further benefits to the guest.
Hilton certainly welcomes you to stay with them...but you have to book thru them if you want the advantages of being a Diamond.