Really interesting question ! I cannot speak for him, because each stutterer and relation with a stutter is different. But I can still give you a point of view of a stutterer : On my side, I will feel flattered and reassured, if a girl tell me that she finds my stutter attractive, I will be relaxed when I talk to her, and speak more freely. But I will not like to be reduced to it. My stutter is not something that you want to keep, it's not something that should make me "more sexy". It can put in weird unconscious dilemna like : "I want to speak without a stutter, but my girlfriend find it sexy, what do I do, if I don't have it, am I not sexy anymore ?" (but that's only my thinking, for your boyfriend it could be totally different). + saying that it's a good quality, can be quiet harsh (but here same, only on my side maybe). From my side for example, an ex-girlfriend was always saying : "your stutter is ok, it's not a big deal, you are good like that no worries !". I know that she was doing that to make me feel better. But actually, I felt even worst, and more distant with her, because saying that a stutter is nothing is like bypassing everything a stutterer have been through, I felt like she didn't understood me, and that was actually true. My final advice will be to say him / make him feel that his stutter doesn't bother you (talk normally with him, don't finish his sentences,...), so he can talk freely to you, and try to understand how his stutter have impacted his life, then you will be able to know what is good for him. But I think you are already in the good way, asking your question was already a really great thing !!