I'm a multi-year Gold member and I travel in economy from time to time. I'm wondering if any other Gold card holders have noticed inconsistent treatment from the inflight crew whilst traveling in Economy. Sometimes I've been given a glass of champagne as soon as I've taken my seat, had priority meal service, etc and other times I've been duly ignored. What have you guys experienced? Is there an "official" policy?

No official policy as such.. there has been talk a lot on here of late regarding service inconsistency in the dealings with FF s.
A few months back I understand there was a memo passed to the FSM and CSS directing them to make time, if possible, to welcome back the AU and AG members, although it is a flip of the coin kind of thing as to whether or not you will get a hello and thanks for keeping your business with VS.
I've had similar experiences to yourself, it is never certain. Always love a welcome back and thanks for flying convo as it breaks the ice and allows you to talk to the crew on a more personable note. It elevates the service offered to a more personal level which is def appreciated in my book y)