The result may be the same, but I think honour requires a state of mind where you do the "honourable" thing even if nobody will know.

Agreed. Honor may have its roots in a prisoner's dilemma, but you're not actually practicing it until you have Stockholm syndrome.

"states of mind" are all externally influenced. If you have a fundamentally "honorable" mindset, it's because your history has reinforced that acting honorable nets you an overall positive outcome.

Which just reinforces the "honor = iterative prisoner's dilemma" argument.