What is „market manipulation“ actually vs non-manipulative buying and selling to make a profit?
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This example has two common characteristics of market manipulation - using size to push markets in a direction for personal benefit, and putting the bid in with sole intent to push the market, as in there was never any desire to see the order actually get filled.
If Jane Street was selling options that were only profitable within the context of a strategy that involved pushing massive size into the market near market close and forcing price down, that is likely categorized as manipulation. On the other hand, if they were moving inventory and in the process moved price, and they tweak their trading strategies to further profit from this, that's a more arguable position.