Jack is not upset because he couldn't buy the shares at the price he wanted. He is upset because someone was offering shares at a specific price, and Jack was willing to pay that price, but the order was not executed. The reason the order was not executed is not because someone else accepted the offer before him, or because Jill cancelled before he tried to accept. It was because Jill was able to see his acceptance in transit and cancel part of her offer as a result of this new information. This isn't how markets are supposed to work. If Jill had posted a single offer for half the number of shares that Jack wanted, it would be different.
Someone shouldn't need to use Thor or some other delaying mechanism to accept open offers. The latency between different exchanges (which was exploited in this example) does nothing to increase market efficiency.
You're right that I shouldn't care about this as a practical matter, as the impact on me is very small, but that doesn't mean it's right.
I really appreciate the clarity in your comments on this thread.
Someone shouldn't need to use Thor or some other delaying mechanism to accept open offers. The latency between different exchanges (which was exploited in this example) does nothing to increase market efficiency.
You're right that I shouldn't care about this as a practical matter, as the impact on me is very small, but that doesn't mean it's right.
I really appreciate the clarity in your comments on this thread.