[JumpCrisscross]

> nicest houses I know are owned by traders who know how to use technical analysis

On the sell side, sure--you know when they'll under or overpay. Anyone buying retail flow should be running these models.

Technical analysis just looks at the surface of the order book--the transaction layer. If you're integrating the book, you can see when the surface is misleading and profit from it. There are technical heuristics, e.g. dead cat bounces, round-number tendencies, et cetera which are based in reality, part flow of funds and part psychological. But technicians' sole reliance on stock charts necessitates blindness to those underlying conditions.

In summary, a stock's near-term price history can, on its own, provide information that predicts the next tick. It's just a known subset of a broader set of signals. That the delineation is known makes those relying on these strategies possible to arbitrage.