I think the person you were responding to was being a bit facetious.

Additionally, the comment saying you don't matter has a bit more nuance than that. You literally do not matter enough to some minimum wage fast food worker to "get revenge on." They're just going to remake your food. Even if you were trying to dupe them somehow, the regular workers literally do not care. They aren't paid enough to. The manager is the only one who might give a shit and they certainly aren't going to be spitting in your food.