Butt-baring formal wear?
When I was twelve or thirteen, I was at a friend's bar mitzvah party in the southern U.S.→
[More:], a very ritzy affair because my friend's parents were very wealthy and his father was a prominent businessman.
My friends and I were astonished to see a woman dancing in a black lace-backed dress with no panties on. We saw her buttcrack. It was plain as day. We did a double-take, triple-take, quadruple-take. There was no mistaking what we were seeing. I don't recall seeing her "front" and I'm assuming it was not as revealing. This woman was conducting herself as if there was nothing inappropriate about her outfit.
My question: Is it considered appropriate to show your butt in a formal setting if it is at least covered with very transparent lace? Is a butt-baring women's formal dress "a thing"?
I ask this because I was at a wedding reception tonight and this memory, long forgotten, came back to me. Neither I nor my girlfriend could fathom this being an acceptable mode of dress in polite society ... but maybe we are wrong?