I'm glad I don't feel alone in this. I think it's people's go-to phrase because they think it's what stutterers want to hear – so their intentions are in the right place, but as you said it comes across like they think a feature about you is taboo. For now, my response is just a defeated smile (which is a lot better than my previous response, which was to thank them lol). If I'm brave enough, I'll say "yup, years of speech therapy."