Tattoos can be cathartic... for me anyway. I have a lot of very large ones and while yes I find them addicting. I don't think that they are in any way to be confused with si. Self injury is for the purpose of self loathing, confusion, to sooth bad feelings in a very destructive way. Whereas tattoos are an expression of creativity, love of art, and just plain enjoy the pain. My wife "Laura" says I am a walking ,talking contradiction. I think the pain is a form of payment for the ink. Which is really good art...
Michael