His statement: “If the host assigns him a place, he should not go beyond it.”
This is part of proper etiquette. Thus, if the host says to him, “Please, sit here,” he should not say, “No.” However, if he is a man of distinction and standing, and the host seats him in a place unsuitable for him, then he may decline, because the host has not honored him; and where there is no honor, there is no courtesy owed.
If the host says to a person entering, “Sit here”—meaning, at the head of the gathering—but the visitor would prefer to sit elsewhere, where he can be close to all those present, is he then disobeying the host, such that we say, “There is no harm in it”? Or do we say: You entered by the host’s permission, so you have no right to sit anywhere other than the place he assigned to you?
The answer is the latter. But if he sees it to be in the interest of the gathering to sit among the people rather than at the front, then he should ask permission.