Catholics theologians have for centuries beginning with the practice of the early disciples believed this was the foundation for the sacrament of confession. Indeed, the theological support for this is overwhelming.
http://www.catholicfaithandreason.org/confession-of-sins-—how-biblical-is-it.html
The key to your understanding is you are putting your faith in CATHOLIC theologians. There are plenty of other theologians who disagree with those, so the question becomes who is right?
Well the key to that is 1) being saved and having the Holy Spirit to guide you and 2) studying the Bible yourself.
Another simpler understanding of “to loose or bind” one relates to Jewish Priests who could “loose or bind” people brought before them for breaking any number of the minor laws constructed to uphold the greater laws. An example of this was sabbath laws. A person could be brought before a priest for say walking farther then a “sabbath mile” on the sabbath and the priest could hear the person out and decide if the reason the person gave was good enough to “loose” them from the consequences or “bind” them to it.
This authority to “loose” or “bind” was given to all of Jesus’s diciples who would lead the first Christian churches and it was about setting up minor church rules and the ability for the church leaders to flexibility in enforcing those rules.
So if I agree to my church’s rule of not playing cards, but someone finds me playing cards, the church can discipline me or not based on what they find out and Christ will honor that decision as being just in Heaven EVEN though there isn’t anything in the Bible against playing cards.
IF that verse meant that a mortal could interfere with someoneelses salvation then that would contradict so many scriptures which say things like: “WHOSOEVER calls upon the name of the Lord SHALL be saved.” Romans 10:13
Salvation doesn’t come through a physical consumption of communion, it comes through repentance and faith.