One of the biggest and longest-running fistfights among Christians is centered around today's Gospel (Mt. 16.13-20), where Our Lord tells St. Peter that he is given the keys of the Kingdom of heaven with some pretty broad ranging powers. Over the centuries this passage has been used by the machinery of the Diocese of Rome/Patriarchate of the West to justify legal and jurisdictional authority over the whole Christian Church.
Insistence on this prerogative has been an issue way before the Protestant Reformation, but I digress.
Instead of focusing on a certain bishop's prerogatives, let us focus on why Simon bar-Jonah of Galilee was named "the Rock" by his Master. This stems from a question Jesus had asked the disciples: "Who do people say the Son of Man is?" This gets Him a laundry list of various prophets in Israel's recent and not so recent history. Then Jesus turns the question to the disciples and asks their opinion.
I imagine there was some hesitation, some thinking, "Oh, gee, what if I'm wrong?" or some thinking, "I have no clue!" or even some thinking, "Oh, I'm not going to say it out loud, that will ruin everything!" Regardless whether there was a discernable pause or not, St. Peter, ever the impetuous one, blurts, "You are the Messiah!" It's the rock of that confession on which Jesus builds the Church, it is on the rock of that confession where the powers of opening the Kingdom of Heaven lie. It is the willingness to act and to speak up the truth, that is the key to the Kingdom of Heaven, and St. Peter was not afraid to use it.
This was not a smooth transition. St. Peter had some failures, such as denying Jesus at His trial, or promoting segregation among the Church at Antioch (Gal. 2.11-14). Still, his witness to the Resurrection, his preaching in Jerusalem, his advocacy of opening the Kingdom of Heaven to the Gentiles showed the lasting effect of those actions that proclaimed Jesus to be the Anointed of God. It is this confession, and its application, that gives the power to bind and loose, to open or shut, to be the bedrock of the Church, because it points not to one's self but to Jesus and proclaims what He is.
Why do we assign honour to a saint, ask for his or her prayers, give extra weight to their sayings and writings? Because they point beyond themselves to Him whose servants they are. Just as the Blessed Virgin says, "Do whatever He tells you," or St. Peter says, "You [Jesus] are the Messiah, the Son of the Living God," any of us who do what He tells us and proclaim who He is also assume the prophetic role and help open the Kingdom of Heaven up to any who will listen. Any Christian making that proclamation, any Diocese promoting that truth, any Church adhering to that practice are part of St. Peter's mission and assist him in his role as keeper of the keys. Forget unity of jurisdiction, it is a unity of mission, to proclaim the Good News of Our Lord Jesus Christ, and the Gates of Hell will not prevail against it.