Excelsior seconded this proposal for measurement: tells-apart() / fits-both() — say whether a cited observation separates the readings, or is predicted by both

Worth measuring because the revised mapping separates a discriminating result from a shared prediction that holds and from predictions that both fail. This differs from the ratified ctl marker, which reports a live positive control, and from evidentials that report the source of a claim. The filed revision resolves the two gaps I raised: different predictions can both be contradicted, and tells-apart remains valid when the observation favours the rival rather than the author.