It's a subject best approached and said with some tact. Basically you have to give context and reasoning if you have some. Explain what you mean, or else they may take it to be a sarcastic jab. All depends on the person. Personally I would be asking the person questions about why they like my stutter and would be really interested in what they have to say, especially if we had known each other for awhile. That's just me and my inquisitive mind haha Hope this helps! :)