**I tend to think of Matt 16:18 like Augustine. Obviously the “unanimous consent” of the fathers was absent in the understanding and translation of this verse in the early church. **
"In a passage in this book, I said about the Apostle Peter: ‘On him as on a rock the Church was built’…But I know that very frequently at a later time, I so explained what the Lord said: ‘Thou art Peter, and upon this rock I will build my Church,’ that it be understood as built upon Him whom Peter confessed saying: ‘Thou art the Christ, the Son of the living God,’ and so Peter, called after this rock, represented the person of the Church which is built upon this rock, and has received ‘the keys of the kingdom of heaven.’ For, ‘Thou art Peter’ and not ‘Thou art the rock’ was said to him. But ‘the rock was Christ,’ in confessing whom, as also the whole Church confesses, Simon was called Peter. But let the reader decide which of these two opinions is the more probable" (The Fathers of the Church (Washington D.C., Catholic University, 1968), Saint Augustine, The Retractations Chapter 20.1).
"And I tell you…‘You are Peter, Rocky, and on this rock I shall build my Church, and the gates of the underworld will not conquer her. To you shall I give the keys of the kingdom. Whatever you bind on earth shall also be bound in heaven; whatever you loose on earth shall also be loosed in heaven’ (Mt 16:15-19). In Peter, Rocky, we see our attention drawn to the rock. Now the apostle Paul says about the former people, ‘They drank from the spiritual rock that was following them; but the rock was Christ’ (1 Cor 10:4). So this disciple is called Rocky from the rock, like Christian from Christ…Why have I wanted to make this little introduction? In order to suggest to you that in Peter the Church is to be recognized. **Christ, you see, built his Church not on a man but on Peter’s confession. ** What is Peter’s confession? ‘You are the Christ, the Son of the living God.’ There’s the rock for you, there’s the foundation, there’s where the Church has been built, which the gates of the underworld cannot conquer (John Rotelle, Ed., The Works of Saint Augustine " (New Rochelle: New City Press, 1993), Sermons, Vol. 6, Sermon 229P.1, p. 327).