Selling order flow refers to the exact mechanism IB just described. It&#x27;s mechanically no different from a dark pool (such as IEX, the heroes in Flash Boys).<p>If you have evidence otherwise, by all means post documentation <i>describing the specific mechanics of how matching works</i>. Simply citing news articles that use the word &quot;sell order flow&quot; doesn&#x27;t count.<p>I just cited IB because their docs are very detailed and because I know them well.