An AI is just code: If the AI has the ability to write code it has the ability to self modify.
If the AI has the ability to write code and the ability to replace parts of itself with that code, then it has the ability to self-modify. This second ability is what I'm proposing to get rid of. See my other comment.
If the AI has the ability to write code and the ability to replace parts of itself with that code, then it has the ability to self-modify.
Unpack the word "itself."
(This is basically the same response as drethelin's, except it highlights the difficulty in drawing clear delineations between different kinds of impacts the AI can have on the word. Even if version A doesn't alter itself, it still alters the world, and it may do so in a way that bring around version B (either indirectly or directly), and so it would help if it knew how to design B.)
If it's worth saying, but not worth its own post (even in Discussion), then it goes here.