In Mishima’s The Temple of the Golden Pavilion, the protagonist Mizoguchi has a stutter. At one point, it is suggested that stutterers speak more fluently in a second language.
That piqued my curiosity. At first blush, it looked like it could be true and many people on forums say as much. There’s less pressure to speak perfectly, and speaking slowly and deliberately comes with the territory in the early stages of learning a language. The dislocation of a new language can also feel like acting, liberating the speaker from their normal persona. And in a similar vein, the second language lacks the emotional baggage and trauma associated with speaking in the mother tongue.
However, unfortunately it’s a largely temporary phenomenon. As the speaker becomes more proficient they are likely to begin to stutter more. The underlying stuttering is not cured.