I know a woman who laughs after virtually everything she says, although I do not recall her ever saying anything funny. Like an exclamation point at the end of every sentence, this creates a boy-who-cried-wolf effect. If she ever does say something funny, how would anyone know?
So what does that tell us? When comics like Steven Wright and Rodney Dangerfield are introduced to an audience, everyone knows they are supposed to be funny, so everyone feels free to laugh. For the rest of us, some compromise may sometimes be necessary. That compromise, like the occasional exclamation point, can simply be a broad smile that warns everyone it's only a joke.