Evening Isiah,
I just tested several of the other Text Codes from Yanfly's Message Core and your suspicions were correct!
I just tested several of the other Text Codes- \N[n], \Gm \C[n], \} , and \{, - all of which worked correctly, with the noted exception of \I as you theorized.
Let me know if I can be of any other assistance and thanks again for such a speedy reply.
-Koa