That's why I called it a hack. Fundamentally, it's not much different to gambling with an advantage - there were certainly a lot of opportunities for him to lose.

I don't think this called for a suspension of ethics, rather more of a disregard for the establishment.

Look, legally exploiting a flawed system to produce a net benefit for oneself isn't fundamentally evil. In fact, in this situation it seems (fortunately) that his actions eventually bailed out a whole lot of small-time investors.