No, because if you short at close on ex-dividend and buy back at open the next day, ceteris paribus you gain the stock price delta (which is exactly equal to th

No, because if you short at close on ex-dividend and buy back at open the next day, ceteris paribus you gain the stock price delta (which is exactly equal to the dividend), but you also owe the amount of the dividend to the person you borrowed the stock from. You end up netting nothing.