I don't find what they did particularly rude. And Bitt, you're assuming that the most common configuration of people sitting at the bar is two people. I don't think I've ever eaten at a bar with another person. I think couple 1 could reasonably expect a single person to sit in seat A.

Along the same lines, what if there's a single person in seat E? That person could move to A, but it's not likely.

I would definitely wait for that couple to leave. The amount of time to eat dessert would be far less than an hour wait (which I'm completely used to in my area), and I think it's unlikely that the couple would sit at a bar for a long conversation afterwards.

Anyway, there are much more annoying practices from restaurant patrons. I've been in a party of four at a crowded restaurant with a long wait. Almost all the tables are four-person booths. I'm standing with my party by a freezing cold entrance, and 12 feet away there's two people occupying a booth who have clearly finished their desserts a long while ago and are now just chatting away. I find that rude.

Similarly, my favorite breakfast place has extremely busy weekend mornings. Nearly every week I'll see someone who obviously came in before the rush, but has decided that he has every right to sit alone in his four-person window booth and read the paper and have cup after cup of cofee, even though there's a line out the door, and will do this until the lunch period starts. Will they move to one of the two-person booths which are essentially for one person? Nope.

Damn, why'd you start me on a rant?