The keeper board and league history are for the twelve managers in this
league. Signing in with the Yahoo account you play under confirms you are
one of them.
Your Yahoo account stays yours. We ask Yahoo once whether
the account you sign in with is a manager in this league, and then discard
the answer's credentials. Nothing is stored about you beyond a cookie saying
you are signed in, and league data is read using the commissioner's own
Yahoo access, never yours.