The way you came off was kind of rude to people who have been dealing with stuttering their whole life. The idea that someone would need their stutter pointed out, like they would have no idea about it. The amount of anxiety, stress and shame is causes people - they literally think about it every day of their life. It sounds like if your Dad does stutter, he has a pretty good handle on it. If people who don't stutter have dis-fluencies. I'd say just love your Dad for who is, and if it bothers your, maybe look internally to ask why that is.