I am puzzled by such a statement. An LED connected with opposite polarity represents an open circuit - there is next to no current flowing through it, no power dissipated, so it cannot be burnt. The LED bulbs with standlight from German Ebay are specifically intended for generator systems. While they work with one polarity only, a generator provides both. I have one like that mounted on a bike and the lamp works fine - better than with an incandescent which was the whole purpose.