I saw a thread about visible undergarments and it was timely for me. I underdress almost daily, including a non-padded bra. I don't try to pass and I never try to deliberately show my bra, but I just like to wear these things. And frankly I enjoy the small amount of support that I get from bras.
I was on a flight with my seat reclined (had been upgraded into biz on an international so was almost lying down). My shirt got snagged by something on the edge of the seat and right at that second, the woman next to me looked over and clearly saw my now exposed bra strap. She didn't say anything right away, but then looked over and asked-
Her "can I ask you something... are you wearing... a bra?"
Me (i hesitated for a second) "yes, I am. Are you?"
Her (she waited a few seconds) "Yes. But may I ask... why?"
Me "Same reason as you. I am more comfortable with my breasts supported"
Her "Hmm. OK. Well, good for you for being bold enough to do that"
It was surreal. I was totally unprepared for this conversation.
