This formulation or variant of TDT (I'm not sure if Eliezer's TDT does or not) requires that before a decision problem is handed to it, the world is divided into the agent itself (X), other agents (Y), and "dumb matter" (G). I think this is misguided, since the world doesn't really divide cleanly into these 3 parts. But if this is the approach a decision theory researcher wants to take, they should at least acknowledge the "recognize myself and other agents in the world" problem as a problem, and say something about how this might be done in principle.