hope I am not too late everyone as everyone in here has said, everyone is different. For me, i dont mind other finishing my words as long as A) it is an attempt to help and not an act of impatience, or B) it is is a *good* friend throwing out words i am obviously not trying to say in order to make immature/dirty jokes. Remember, his stutter is a part of who he is. Accept it, joke around about it the same way you would anything else (like being clumsy or bad sense of direction), but at the same time dont be a jerk about it. EDIT: I just reread your TL;DR and realized it was a first date. in that case i would just pretend it didn't exist, unless he is *extremely* stuck (as in, runs out of breath before he gets the word out); in that case finish it for him then forget it happened.