If I recall correctly, the Lauda Air B767 accident over Thailand some years ago was caused by one thrust reverser deploying during the climb at around 28,000 ft and mach 0.76? - and at night.
I understand that the crew had less than 5 seconds in which to shut down the engine before they lost complete control. It was an almost impossible situation to be faced with. Presumably the reverse thrust plume that destroyed the lift over the affected wing was phenomenal at that speed. If the event had happened at the same IAS at a lower altitude, would the effect of the reverse thrust on the aircraft behaviour have been changed significantly?