I've noticed when I'm in public, say at a restaurant, and someone I know walks in, I'll pretend not to see them. I'll put my head down and read the menu, or look away so not to be seen. I've also noticed that people do the same thing to me.
I'm not sure why I do it. I'll be the first to admit it's strange. Maybe it comes from having awkward conversations in the past. Or maybe its as simple as not wanting to be bothered, or not liking the person in real life.
Whatever it is, it's weird. It takes a lot of energy to look invisible. It'd be easier just to wave and give the forced smile and then have the uncomfortable conversation at the restaurant table, where inevitably, somebody is standing and somebody is sitting, someone is looking up, and someone is looking down.
It's hard to say what's better. All I really want, is to eat in peace.