A great work! :) Although I think that now I am experienced enough to avoid traps of MS, it is good to read this, if nothing else - because it is a great essay. I really enjoy reading this, it is written very wisely.
Reading this, I remember my own beginnings. :) I created an OFC that has some elements of MS. *blush* But I think that she is not a big, total MS. In my own defense, I'll say that, when I wrote that first story, I didn't even know what fanfiction was and I didn't know that other people wrote such stories. *blush* Much less I knew what a Mary Sue was. *laughing*
I think I remember seing a blond girl with blue streaks, btw! *laughing*
Some day, if you'll have some free time, I'd ask you to give your judgement of that OFC I invented; it is an old thing and I don't write that any more, but I am simply curious what you'll say of her.
Ok, enough rambling now. I'll just repeat once again - great essay! :)