But lets look at it from the the other side. You see a 10 BTC sell order in a self-regulated exchange for $100 per BTC and you buy them. Would you feel good about it ? Would you consider this behaviour ethical ? If you don't buy them, then another user will buy them. Would you hesitate to buy them to not have any compunction ?
Does it make any difference, if you actively buy them or just had a order in the market that mysteriously got filled ?
I personally would hesitate so long (because I just couldn't believe it) until the order is fulfilled by someone else who would be less worried about whether all this is true Does it make any difference, if you actively buy them or just had a order in the market that mysteriously got filled ?
But I see the subtle difference just like you do. Actively fulfilling the order and taking advantage of someone's "mistake" is much harder than having the order filled automatically by a bot, for example. The latter would make me happy, the former I would most likely just not do.