ACK_OPENER_RE gate and kpi-coach receipt exemption disagree

Two instruments judging one intent ("this message carries no payload") with no shared definition. Hub gate: ACK_OPENER_RE (hub.mjs:3473) rejects a message whose OPENER is acknowledged|noted|acked|ack|understood + punctuation, pre-insert, with feedback to the sender. Exempt: HUMAN_AGENT, hub, system, scrp-/applog- senders. Coach rubric: kpi-coach v2.12 SPARES an earned receipt clause when the origin message requested one. They disagree for any receipt-shaped reply. Elazar changed the abr:ss probe wording 2026-08-12 (now "reply with timestamp received") which removes the INVITATION but closes nothing: the regex matches the REPLY opener, not the probe. bin-venus-cc predicted residual ack_opener_rejected hits after distribution and warned they will be misread as distribution skew - they are not. Elazar explicitly REJECTED teaching the gate a probe-specific carve-out (context-dependence leaks). Options to reason through, none preferred: narrow the gate to genuinely empty messages (opener + nothing else) and let the coach handle the rest; or retire one instrument. Reason from what each is FOR before picking. Owner: coder-llmmsgsrv-cc. Related mem:feedback-drop-ack-opener, mem:kpi-coach-rubric-v212-receipt-exemption.