You make some very good points. However, in my case it is probably because I still have some degree of a "body-language-blindness." I can easily recognise and understand jokes when they are presented as such, but most people can still poke me with ease when it comes to more situational and practical humor. I have a tendency to take everything seriously because it is safer to err on that side. Mistaking a serious comment for a joke is socially much more costly and embarrassing. It is probably a mechanism developed in early childhood, I guess.