Haha guy here, just got done with high school, so I'd be quite suspicious of anyone who could possibly find a stutter hot; I'm sure it's possible, but after 10 years of flak from family and classmates, it's hard to associate the sole thing that holds me back with being"hot". That said, it'd probably depend more on my relation with you: if we were friends or good acquaintances, I would take it as a compliment but if we had just met and you struck me as cocky, then I'd assume you're mocking me and get annoyed, unless you made it clear you aren't mocking me. But that's just me, I'm sure there's stutterers who aren't entirely frustrated by their speech who might take it as a compliment.