YOU SAID:
self talker better shut his mouth
INTO JAPANESE
自己話し手は彼の口をよく閉める
BACK INTO ENGLISH
Self-talker closes his mouth well
INTO JAPANESE
自己話し手が口をよく閉める
BACK INTO ENGLISH
Self-speaker closes his mouth well
INTO JAPANESE
自己話し手が口をよく閉める
BACK INTO ENGLISH
Self-speaker closes his mouth well
That didn't even make that much sense in English.