at the behest of starting an argument, But just because this person doesnt talk alot or smile does not make him miserable. Important points allready summed up.
SOP,
Good Operational Communication,
Team leadership, etc.
Might be worth remembering before cracking a funny joke that he might not find it amusing.
Example: My Father passed away last year and enroute back to my home an acquaintance of mine (who I think is a D@@K) cracks "who let you back into the country then". I'll leave the rest up to your imagination.
Regards.