Wow. My best friend has the same condition. Both stuttering and bypolar 1 mania. Last time we went on manic episode we had to call the mental hospital to get him because he was totally gone. Is it exactly as you said it. When on manic episode the stuttering is completely gone. He can talk for hours and nothing. He can be talking to the president or to +1000 people and it does not mather. He is not thinking just speaking. He is not measuring the consequences of anything (besides stuttering, he put himself on danger multiples times). He could not care less of what other people think about him. I mean he go to the park and preach about god and stuff like that. The strange thing is after the episode is gone because of the medication, the stuttering come´s right back. I don´t know the cause of stuttering but for what I seem with the 5 episode of my best buddy is that on manic he has no shame. No filter. No fear. No preocupation of other people. Maybe that´s why he don´t stamble. I hope everything works for you mate.