I've never really thought about it before, but it seems if someone is genuinely asking about the scar then I suppose I can take it as a sign of interest, the same way that someone asking about a hat or furry vest

I've just never really jumped on it like I should I suppose.
As for shaking with the left, I've always used it as a tool to see how observant someone is, ie. if I meet them a second time, and they offer the left, then they are an observant person. If they offer the left the first time, then hell, they are really sharp.
I guess it's all about flipping what most people would see as a disadvantage into an advantage