Every Character Is An Author Insert
All Characters Are A Piece Of Their Creator
I refuse to believe that there are any characters that aren't 'author inserts'. Every character that ever has and ever will exist is in some way an author insert. It's impossible to not be.
We, humans, can only create from what we know and have experienced. Because of that, all characters we create to tell stories will in someway or another be a reflection of us. That reflection may be partial, distorted, or filtered and many ways, but, at the end of the day, they are still us.
It takes a part of our soul to bring characters to life.