=== WHY THE TWO BEHAVIOURS ARE NOT THE SAME THING === "Repainting" gets used for two very different things, and mixing them up is the reason the harmful one goes unnoticed. Intrabar movement. Any indicator built on the current price moves while the bar is still forming and settles when the bar closes. This is normal. It is not a defect, and it is not what breaks a backtest. It only matters if you act on a signal before the bar has closed - and then it matters a great deal, because the signal