For me, It depends on the situation. Like fast food restaurant I would like to hear someone finish the sentence with my order, cuz I don’t want to waste anyone’s time. But if we’re communicating, when I try to express my opinion it’s the best for the listener to wait for me finishing the sentence. Just try not to laugh, I know it sounds funny sometimes, but it must be the most hurtful thing for a stuttering person. Thank you for communicating with us!