Private judgment and sacramental magisterial authority

A commenter named 'Mark' said the following in the combox of this article:

Once you've allowed that the private judgment has the ability to lead you to the source of all truth, what in principle can be wrong with permitting it to have a perpetual role.

'Private judgment' means specifically that the individual acts as his own ultimate ecclesial/interpretive authority. If a person, apart from any sacramental magisterial authority, discovers that there is a sacramental magisterial authority, then if this person continues to act as though that sacramental magisterial authority is not a sacramental magisterial authority, this person is living in a manner that contradicts what he knows to be true. Private judgment is not the same thing as free choice. A person who submits to an authority can do so freely, while not living by private judgment. So a person who discovers sacramental magisterial authority can and should continue to exercise free choice in his acts of obedience to that authority. But for such a person to continue to operate in the mode of private judgment would be for him to operate as if there is no sacramental magisterial authority.

Therefore, just because there is nothing wrong with coming to discover sacramental magisterial authority apart from the oversight of that sacramental magisterial authority, it does not follow that one may operate thereafter as though there is no sacramental magisterial authority. Private judgment is not incompatible with coming to be aware of sacramental magisterial authority, but continuing to operate according to private judgment is incompatible with an awareness of sacramental magisterial authority.