In answer to second part of your question, if you are trading on...

In answer to second part of your question, if you are trading on market ie lit market, just say you've put in a buy at $8.50 and someone has a buy through a dark pool at $8.50 the order placed first takes priority. So there is no preferential treatment for either market. Asx trading rules stipulate that dark trades must be at a premium to lit trades though... although im not entirely sure about the mechanics of how that works although I think I have an idea.