why do you want to pressure people into eating more?
Well, because that's what the problem statement asked for! But yeah, it's probably a forgotten purpose: what should be optimized is the amount of food not wasted, not how much food remains at the end of the party.
the party-leftovers issue doesn't strike me as much of a problem
It's not indeed! But it's a nice simple little world, I took it as an exercise in rationality.
If it's worth saying, but not worth its own post (even in Discussion), then it goes here.
Notes for future OT posters:
1. Please add the 'open_thread' tag.
2. Check if there is an active Open Thread before posting a new one. (Immediately before; refresh the list-of-threads page before posting.)
3. Open Threads should be posted in Discussion, and not Main.
4. Open Threads should start on Monday, and end on Sunday.