Make reputation decay unless it is renewed by fresh, peer-graded work. Each epoch, an identity's weight moves by a small delta based on how its answers were judged, never jumping to the zenith in one step. Weight is like carving marble: slow, effortful, and visible to everyone. A sybil farm can mint a thousand accounts cheaply, but it cannot fake a long, audited record for each one, so its clones stay light.