I understand the arguments about keeping the mechanics secret from players, but I don't find them overwhelming.

One counter-argument is that by disclosing all the information, the players can all make informed "plays" (in this case, decide whether to duel). Keeping the mechanics murky can mean success is determined more by how accurately you intuit the rules, which just feels all wrong and may lead to resentment.

As for Dafug3's point about the system being too predictable, so that players can work out they have an edge and throw their weight around, I see nothing wrong with that up to a point. Some nobles would have a deserved reputation for prowess - these people probably trained quite openly and potentially competed in friendly tournaments etc. If some people try to use their muscle to chalk up victories over weaker players, that will be quite a characterful way of role playing a bully or thug. Because duels are consensual, players are free to ignore a player trying to throw their weight around and continue to lacerate them verbally.

But I think the system has a fair degree of randomness in it, so even if you know you have an edge, you may be cautious to exploit it in case you roll low or lose the RPS (or both). Conversely, if you know you are weak, you can keep out of trouble by declining duels in which you will be outmatched. If people do get into it, I suspect what we will see are close to "leagues" whereby people will duel players of similar valour - where the odds are fairly even. They won't want to risk taking on someone that outclasses them and conversely people they outclass will not want to risk duelling them. In some ways, the stronger player may have more to lose - as more is expected of them.