The messenger of a man like him

Explanation: In one place in the Gemara in the BM (Zo.) appears the phrase "Is the son of a man like himself?", which is a general classification and not just in vows and borrowing from husbands.
But it's difficult, because then why doesn't this controversy appear in the Kiddushin where the origin of the law of mission is discussed? And then you stated that there is no controversy regarding mission, but only regarding the principle that the messenger is like him.
 
And I didn't understand, what does the MD really believe that there is a mission but he is not like him? Does he believe as the MD that the mission of a person is like him but only as a power? It can't be, because then the investigation of the latter is itself a dispute over the aforementioned? Be warned.
In short, what is a messenger without his messenger?