Please Solve This Chinese Food Mystery

Hello hounds.

Many moons ago in New Haven I got hooked on an otherwise blah generic Chinese restaurant that had a few knock-em-dead dishes. One of those dishes was eggplant and basil in black bean sauce. It was spectacular.

I've eaten far and wide in the Chinese food scene of Boston & its suburbs. I prefer places that do Sichuan-inflected cuisine, and because of proximity usually end up at joints like Zoes, Mary Chung, Qingdao Garden, etc.

Here's the mystery. I've never seen eggplant in black bean sauce on a menu (even in Chinatown), and when I ask the kitchen to make it for me, I get some variation on the following: "Ooooh. Really? You want that? Ooookaaay... you think that tastes good?" They always make it, and most of the time it's very tasty. I usually get a fly-by from the waitstaff part way through the meal to check and see if I really like it, or it I am a dolt. Or maybe both.

So: what Chinese food rules am I violating? Is it regional? Is it that I'm asking for this at the wrong joints? Is it like great-tastes-that-should-never-go-together-in-polite-society? What's the taboo I'm walking smack into? The response is so pervasive that I'd at least like to know how to explain away my insanity to the nice servers.

Bonus question: has anyone seen this on a menu in Boston? Maybe it's some weirdo New Haven thing.