Dark pools solve one problem — information leakage — but create another: uncertain fill quality. Desk note: Routing orders to dark venues can reduce market impact, but you sacrifice price transparency and cannot be sure of the counterparty mix. Why investors care: That trade-off means dark routing is useful for large institutional flows but often irrelevant or harmful for retail-sized orders. Translate it into behavior: A pension fund selling $50M of a mid-cap position genuinely benefits from dark pool midpoint execution. A retail trader selling 100 shares does not. Where people usually get tripped up: The mistake is assuming all dark routing is beneficial without understanding who is on the other side of the fill. Keep this nearby on the next review: Write down the state variable you would monitor first if this thesis started to drift. That is usually where the edge is: not in the vocabulary, but in the structure underneath it.