I have never read a confession on Facebook. I do not use Facebook. However, in order to offer an answer, I learned that on April 3, 2013, someone created a Facebook Page called 18+ Confessions. The about page says this if for anyone who wants to confess something, and your identity will be kept a secret.
I must confess (pun intended) I have never read any of the posts but I briefly glanced at a few in order to respond to this question and honestly, I found them mostly stupid. The posts were either in a language I don’t speak, but those that I could read did not seem very sincere or were comprised of silly jokes. There were also a lot of so called confessions having to do with love relationships.