Transparency

The fee is 5% of the total pool, taken once at settlement and capped at the losing side, so a winning bet always gets at least its stake back. Voided markets, and markets with nobody on the winning side, are refunded in full with no fee at all. The 5% itself doesn't move with the outcome. The cap does: in a lopsided market we take the losing side instead, so finalizing for the favourite earns us less, never more.

Double-entry means money is never created or destroyed. Every entry moves an amount from one account to another, so all the balances sum to zero (the outside world, external:…, goes negative as deposits come in). The hash chain is what makes tampering obvious. Change one old row and the head hash above stops matching. We only re-hash the newest 500 entries, so nobody can use this public page to hammer the database. Editing an older row would still show up instantly: every hash after it, and the head hash above, would have to change too. And the balance replay covers the whole table either way.