First post, hi everyone!
As long as the person next to me doesn't smell, I don't care what they wear, Y or J.
A plane is a form of transport. I wear thongs in a car, on a bus, on a train, on a ferry, a plane is no different to me. Some people will say there's a safety reason why you shouldn't, but if women can wear heels on a plane, which need to be removed in an emergency so as not to pop the slide, why can't I wear thongs?
I've never perceived any negative response onboard because of thongs, Y or J. I'll continue to wear them because they're comfortable. I don't need people to approve of what I wear to feel good about myself, I wear what I wear because I'm comfortable and confident in myself. To be honest, I'd never wear a tucked in polo shirt, chinos and boat shoes because that's not me. But I've seen plenty of that in my flying time - each to their own!!
Pack the manners for good service, and leave the prejudices at home!