There are a lot of examples of the differing meaning of a smile when you google it. Sometimes it is simply not appropriate to smile. I'm not sure if there are any culture that sees them as entirely evil, but a few do have a concept of an evil grin, a concept that sits alongside the smiles being friendly. It doesn't seem to be a stretch that a mistimed smile might make you look like a loon and other such differing beliefs.
Of course, when someone tells you his mother died and you smile like an idiot, it surely will not create a positive effect.
The way I understood OP, it seemed as if - in a normal setting - smiling would be frowned upon when talking to people in general in some places... which I find hard to believe.
The way I understood OP, it seemed as if - in a normal setting - smiling would be frowned upon when talking to people in general in some places... which I find hard to believe.