> I like to believe that there's a lot of savvy and affluent couples out there who are buying either moissanites instead of diamonds and choosing not to tell their friends or family about it to avoid the social stigma.

This is so foreign to me. Why do people care? It's just a way to signal wealth and really not much different than a bride price (a cultural practice that American expats are quick to criticize in an Asian culture, for reference). My girlfriend / future-wife and I will get matching steel rings or something similar, like my parents have. She's not American so she was thrilled by that idea. I already told her I won't wear it most of the time because rings are annoying, and again that was no problem at all.

I would run the other way if someone is resolute about buying a diamond, after everything that is known about the diamond industry. It means either that person is totally ignorant of the world around them, or doesn't care about making a positive impact with their lifestyle choices.