I don&#x27;t see an issue with quote matching or pennying someone&#x27;s order on a public exchange. That&#x27;s arguably either providing liquidity in a place where it&#x27;s missing or providing price improvement, and they are at risk on the quote. Even if you are the fastest trader on earth, someone can simultaneously sweep your order and the quote matcher&#x2F;penny guy&#x27;s order, and he&#x27;s SOL. It&#x27;s not free money. You can always bid higher or in multiple places if you really want the shares, or just cross the spread. Nobody has a G-d given right to non-toxic fills on their limit orders.<p>Doing it off-exchange for a minimal improvement is less clear to me. In some markets regulators have limited off-exchange trading to block trades or substantial price improvement as a way to incentivize displayed liquidity and price discovery. That seems more fair but also subsidizes informed traders at the expense of uninformed ones. Spreads tighten as market makers compete to trade with some retail flow, but informed spread-crossers also get cheaper trading with these tighter spreads since market makers lose their option to price differently.