Really? I didn't think of it like that at all. We can tell it's fake, because we actually have stutters. Similar to how stuttering actually is, he stuttered more severely when stressed or emotional, so it makes sense for it to be heavier in dramatic scenes. Also, I don't think it was used for comedic effect much at all, except for the "fucking bicycle" scene. But I feel like that's relatable to us, and I think it gets the frustration of both not getting the word out, and having someone guess the end of your sentence, across pretty well. The stuttering in the book is pretty unrealistic to begin with: Stuttering all through his childhood, it completely going away when he moves from Derry, coming back full-force when he returns, then going away again after they defeat Pennywise. In the book, the stutter was definitely meant to be more symbolic of the effect Derry had on Bill. That being said, the information in the book is decent enough (for the time it was written), and I think the movies portrayed it decently. Though I think the best representation to date is The King's Speech. Once Upon a Time in Hollywood was good too, though it was very subtle. I feel like a non-stutterer could have just missed it completely.