perpetual check


Absolutely 100% no. If you have the drawing resource of perpetual check and other moves lose you should do it. It is not unsporting or poor etiquette, it simply means that the position is drawing and not losing.

30.Qf3+ would have forced perpetual check. Your opponent could have played 27.Qxg8 or 28.Qxg8 which was completely winning, but instead did not exchange queens and allowed you the chance to give perpetual check. To do so would have been punishing his error and indeed is one of the aspects which makes chess such a rich game. There are resources in just about all positions and a good player must both find them for himself and limit them for his opponent.