I would like iptables to disallow the sending of a "port closed" (RST ACK) in the OUTPUT chain.
I am not sure if this is correct:
--append OUTPUT --protocol tcp --tcp-flags RST,ACK RST,ACK --jump REJECT --reject-with icmp-host-prohibited
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Not sure what effect your rule (if any) actually would have; do a DROP instead of REJECT.
See REJECT vs DROP when using iptables.