I think you're seriously overthinking this. Here's the way I see it: Either this person that interviewed you remembered that you were the guy who did XYZ, or he didn't.
If he did, then basically he was incredibly rude to you and was telling you that you won't be a chief resident. Unless this person is regularly a jerk, this seems less likely.
If he didn't, then he doesn't really know you did XYZ. He was using it as an example of how "idiots" do stupid things, as an example of how much better you are.
The whole idea of interviewing for chief spots is a bit strange. As a PD, I know essentially all of my residents quite well. The purpose of a chief interview is simply to find out what the resident plans to "do" with the year (we ask each of our chiefs to pick a project to work on). You've been interviewing for a chief spot since the day you matched / were selected.
That being said, there is nothing wrong with asking someone to put in a good word for you -- i'd just leave the whole XYZ thing out of it. Ask them to put in a good word for you if they think you'd be a good chief, and leave it at that.