It's the wording "your hand is replaced by a weapon" that does it for me. It says "You attach any melee weapon you can use in one hand—mundane, psionic, or magical—onto the end of one of your arms. The weapon becomes a natural extension of your arm, and that hand blends seamlessly into the shaft, hilt, or head of the weapon." Going with the loosest interpretation I can think of, your body being the weapon, your arm (the side away from your body) will end in your body. This can be interpreted in at least two ways: your body has a smaller "you" on the end of your arm, or you form some sort of infinite loop that ends with your body giving way to your body, without actually doing that, if that makes sense at all.
Of course, I wrote this over a year ago, and even by then had lost a good portion of my talent for finding things....