My husband and I have had the upgrade issue come up before when we're traveling. On Delta, it is actually a bit more complicated to refuse an upgrade than to request one since its all automated now. I forgot to call ahead of time and tell them I didn't want an upgrade on a trip where my ticket was paid for and I used points for my husband. I didn't want to part with enough points to put him in first class so I thought that we'd both just sit by each other in coach... he's the only person I don't mind sitting that close to me! Well, I went to the Crown Room, and they said I'd already been upgraded. I offered the FC seat to my husband, who doesn't fly often, and he said he'd rather sit by me. I pressed him like, "you're sure, baby? really I wouldn't mind and you'd have fun... I sit up there all the time... you're totally welcome to take it..." and he insisted he'd rather sit by me. He's great! Anyway, we asked if I could have my old seat back and they gave it back to me. Then, at the gate, the agent was calling my name, and I approached, and she tried to hand me a different FC ticket... I laughed and explained what happened and that I wanted to sit by my husband, but again I gave my husband the opportunity to take it, and he refused. All the gate agents oohed and ahhed over what a sweet husband he was. They gave me my old seat back and called the next person up, who had heard the whole exchange and was thrilled to have the FC seat.
Its nice to be married to somebody who doesn't try to trade up and leave me behind at the first opportunity.