I created a mod that adds new favor jobs. This one is based on FavorJobsMineOre, which uses FavorJobsMineOreShared01 ("I'll buy everything you've dug up.") as the de facto response.
In the game, the NPC will say that line. No problems there.
But if I change the response to FavorJobsGatherWheatShared01 ("Honest pay for honest work."), the NPC won't say anything in the game.