are complete strangers who just happen to be in line near me or in close proximity. Why not? A cheery hello, a compliment on something they are wearing or a lovely feature, or just an observation on our current circumstance waiting in line with a pokey person behind the counter who clearly needs help is usually welcomed it seems.

Most respond pleasantly at least. If someone doesn't respond or seems uninterested or hurried, I just leave them be to respect their space. I find that mostly with a particular type of people. I don't know how to describe them, but their vibe is "leave me alone, I'm not chatty so don't waste my time."

If I was all alone and had to find sufficient human contact externally in those situations, I'd be incredibly sad.

Some people are just AHs to others. I think most of us can recognize them a mile away, but lonely people don't have a lot of options.