Is A Nod Acceptable For A "How Are You?"?

Yes, of course.

Can be. Depends on the situation and who is doing the nodding and how well I know them.

I tend to purse my lips & flick my eyebrows in that jaunty little sailor way, so yeah whatever.

In certain situations where talking is limited

I try to tie a smile with my nods.

Sure.

I do it all the time in a crowd or at a distance. I don’t like to draw attention to myself in public. They either get it, or they don’t. Most of them get it.

Not really. If I ask someone a question I expect some kind of vocal sound back, not just a nod.