So I send you… an excursus. “Peace be with you. As the Father has sent me, so I send you.” 22 And when he had said this, he breathed on them and said to them, “Receive the holy Spirit. 23 Whose sins you forgive are forgiven them, and whose sins you retain are retained.”
How one already understands and practices their faith forms parts of lens with which one understands these three simple verses. When I quiz Catholics about who is meant with the plural “you” in these verses, the most common answer is “the apostles.” Behind the answer lies the Catholic church ecclesiology (understanding of what it means to be church) and the sacramental understanding of confession/reconciliation. Those in the Protestant and Reformed churches would not agree and (in general) understand the “you” to be all disciples.
Gail O’Day’s  points out: “It is important to note that these verses identify those gathered together with the general term “disciples” (mathētai, v.19). They are never identified as the Eleven (the Twelve minus Judas), and it is a mistake to read this gathering of disciples in the light of the more closed notion of the Twelve that operates in the synoptic Gospels (e.g., Matt 28:16–20). The Fourth Evangelist rarely speaks of the Twelve (6:67, 70–71; 20:24). The gathering of disciples in vv. 19–23, like that at the farewell meal, probably included the core group, but there is no indication that it was limited to them. This gathering of disciples, like that in chaps. 13–16, represents the faith community in general, not the apostolic leadership.” [ “The Gospel of John.” New Interpreter’s Bible. Ed. Leander E. Keck. Vol. 9. Nashville: Abingdon Press, 2004]. As O’Day already has noted, behind all the answers is also a preference for one gospel over another.
There has been (and will be) lots of discussion about who the evangelist intended as “you.” While clearly plural, the question is whether the intention was to address the apostles present, a wider group of disciples that may have been present – John never enumerates the people in the room – or an even wider audience of believers. Who is intended to go on “mission” (v.21), who was to receive the holy Spirit (v.22), and who was to carry the power to forgive sins (v.23). Fr. Raymond Brown (1034-45) writes:
Some would argue from 21 that the disciples cannot represent all Christians, for this verse refers to an apostolic mission; and even if historically the apostolic mission was entrusted to a larger group than the Twelve, nevertheless all Christians were not apostles (see I Cor xii 28-29). Yet in 21 John has modified the apostolic mission by making it dependent upon the model of the Father having sent the son, and usually for John the Father-Son relationship is held up for all Christians to imitate. Can we be certain that John means “As the Father sent me, so do I send you” in a more restricted sense than he means “As the Father has loved me, so I have loved you” (xv 9)? Nevertheless, even if 21 does give some support to the idea that only the Twelve/Eleven are in direct view, vs. 22 points in the opposite direction. As we shall see, this verse recalls Gen ii 7 and is meant to symbolize Jesus’ new creation of men as God’s children by the gift of the Spirit. Certainly this re-creation, this new beginning, this gift of the Spirit is meant for all Christians…. However, it would be risky to assume that this same widen horizon is in mind in vs. 23, which is a modified form of an ancient saying of Jesus.”
Fr. Brown continues (1040-45) with this latter thought by pointing to Matthew 16:8 and 18:18 wherein the power to bind and loose are given to the limited group of the apostles and the context seems clear that this involves not only community discipline, but also welcoming members back into the community, as well as placing someone outside the community. Such responsibility would also include the formal authority to forgive sins in the name of the Lord. Fr. Brown notes that the meaning, extent and exercise of the power to forgive sins has been divisive in Christianity. The Reformers of the 16th century and late held that the power to forgive sins was offered to each of Christ’s faithful. The Catholic position remained the same as it had been for centuries, that the power to forgive sins was retained in the Sacrament of Penance and was exercised by ordained priests.
As Fr. Brown points out, on the basis of Scripture alone, there will be no conclusive argument made. Each interpretive position relies on other held beliefs and interpretations of the meaning and intent of other passages of NT Scripture. The Catholic position was indeed universal for well more than a millennia in the faith, practice, tradition and teaching of the church. The Reformers would say that it is never too late to correct an error. At the core of every interpretive position is a held ecclesiology, i.e., how one understand “Church.”