Tbh in my mind anyone with a stutter or speech impairment of any kind actually makes me respect a person so much more than most people, as I understand how hard it is for people to be listened too and speak in general. I don't think I'd go out of my way and say that to their face as they'd probably find it strange. Personally I don't think it's something that is likeable, some people may find it weird but if they don't find that it bothers them then I'd highly doubt it would come across as likeable to someone, they would just view it as something that wasn't unlikeable if that makes sesne