I know, the layout is similar to several archives I've already used. They are fairly user friendly too, though I know the Slashy Santa site had strange formatting issues last year. There seems to be a strong preference for the website though!

Archive of Our Own does let you edit your stories. I have an account there I set up when it first opened, and I've edited my stories sometimes immediately after I post them! It's pretty user-friendly once you get the hang of it.