When I check in online it always says "choose your room now and we'll do our best to upgrade you when you arrive" or something like that.

I've always checked in online to avoid being left with the junk if the hotel is busy. In most cases, in dozens of countries, I've been upgraded at check-in as I expected.

Hilton Sheffield (GBR) on the other hand have never upgraded me. Even when I can see premium rooms available they just say sorry we're full...

Today I found out that their policy is to not upgrade any guest who has checked in online. That is how the staff are trained.

Hilton Sheffield has several other big problems, but this for me is the worst (worse than breakfast not starting until 7am, the smell in the rooms, the noisy service elevator, the slamming doors, the unfriendly staff, the feeble showers, the dirty carpets, the aging bathrooms, the lack of privacy curtains in rooms overlooked by office blocks...)

Their policy that you are not eligible for upgrades if you check in online contradicts what you are very clearly told when you check in online. It means that you have to choose between the possibility of an upgrade where available on arrival, or having a little certainty that you won't be left with a room next to the elevator or overlooking the smokers who congregate outside the bar.