Meikleour,
Your response to Bkdoss is absolutely correct. As most people know, the fan is connected to the LPT. One can start the fan and LPT rotating using a finger, that is how good and balanced the bearing system is. With a tailwind entering the exit end of the LPT, it turns the LPT in the opposite direction of intended design, thereby turning the fan in the opposite direction as well. Besides the points you mention regarding the HPC and HPT, I don't think the energy of a tailwind ever gets that deep into the engine, the energy is dissipated in the LPT. As you point out there is no mechanical stress on the engine.