The only reason retail orders actually get matched up well is because they're flagged as retail, are known to contain less information, and are a statistically good bet to transact against. Fundamentally, this was around before HFT and still is. The funny thing is that even if it's helping them in this small way, the whole idea of retail investing is some of the best marketing in the face of contradictory facts I've ever seen.
Please elaborate. If an order makes it to an exchange and that exchange has a bunch of small orders at all times, how is the retail-ness of the order relevant at all?
I understand that at other parts of the order chain this might matter. But inside the matching engine there isn't "retail priority".
Inside the matching engine, there's a sitting limit order on the limit order book flagged as a retail order, just off the bid/ask. Whereas you may not have taken the other side of that resting order before, you might now because you know it has extra informational value attached. Dealers will pay exchanges for the right to access this information, either outright or in reduced liquidity rebates they would normally otherwise receive (normally outright to my understanding).
