To be fair, the reviewer (in the full review on TA) admits that the lounge car was in complete darkness throughout the journey, suggesting a complete power failure. In these circumstances, allowing members of the travelling public to sit in it would almost certainly be a no-no on health and safety grounds (it has no working lights, heating or air-conditioning for a start- even if it’s daylight, what happens when the train passes through a tunnel, and a passenger injures themselves by walking into the wall partition because they can’t see properly?). Even if they could perhaps have expressed themselves more politely, the staff are clearly in the right upholding these safety precautions- they’re there for a reason. If the lounge is merely closed due to a staff shortage, and the lights, heating and air conditioning are working properly, they may well let passengers use it as a seating area.