"Would you only eat the food you buy?" sounds manipulative to me. I much prefer asking "why did you eat my food?" Eating someone else's food is not acceptable. There is a wrong person in this scenario.
Amusingly, "would you only eat the food that you buy" was a suggestion by another person for a less manipulative suggestion. What most people took issue with wasn't the "only eat what you buy" part, but the "would you be willing to <actual request>?" part, which many people took as forcing the other party to answer "yes".
Again, if you're coming from the preconception that someone (normally the other person) is "wrong", you shouldn't use NVC. Earnest NVC requires that you not assign blame or fault. That's the entire reason that you speak only about your feelings and needs and perceived actions of the other party. Granted, "It upsets me when I get to lunch and don't have anything to eat, would you stop eating my food" is also fine in the NVC framework, as I understand it.
> "why did you eat my food?"
This doesn't begin to solve the problem, you're not yet addressing the conflict. In fact, you haven't necessarily signaled that there even is a conflict that needs to be addressed. And note that you're putting the other person on the defensive by not being open about what your goals are. You're acting from a position of uneven information instead of earnesty.
> To me the issue of asking "would you" sounds like the request is optional and they can say, "no I won't". In this case there is no negotiating.
If the answer is no, then like I said, negotiation probably won't work, so you escalate. The point of something like NVC is to avoid escalation when possible. Sometimes it isn't possible.
Another way of putting this is: NVC assumes good intent. When that assumption is invalidated, other strategies are superior, but you lose very little by assuming good intent for a while.
