[Maursault]

> Pain is a signal of impending damage/injury, or existing damage/injury that may well worse if not dealt with immediately.

Pain is not necessarily associated with injury.

>All signals within a human nervous system can be mistaken in principle. Why would this one be different? Phantom pains that indicate no injury seem plausible.

What would phantom pain feel like? Would it hurt? Then it is incidental that it phantom and is nevertheless pain. If you believe you are in pain even if there is no stimulus associated with it, then you are in pain. You can not mistake pain regardless of whether it is "real" or not. What makes pain so special? It hurts, it is painful.