Only if the warnings come up too often. I imagine it should be quite possible to define criteria that discriminate selling shares at a price of 0.0000016 yen fr

Only if the warnings come up too often. I imagine it should be quite possible to define criteria that discriminate selling shares at a price of 0.0000016 yen from normal prices, by comparing with the market price, or the range of prices ever seen by the software, for example. Alarm fatigue is an important design consideration, but not a reason to not put warnings at all (given that this isn't amenable to an "Undo" button, which is preferable when possible).