It's pretty clear that *some* folks just plain don't ever want two Dukes fighting for each other, and are weaseling rationalizations to avoid coming out and saying that in as many words.

You allude to it, but I'm going to come right out and say it: it's very telling that someone, somewhere seems to feel that "superdukes" could never, ever be inspired by someone of their own gender. Or, indeed, find it far fetched that two Dukes could fall in love. What does that say about how we mentally separate "great fighter" and "same sex consort"?

You allude to Duchess Rowan, and so I had to go look it up, to make sure. I think it needs to be explicitly stated that the creation of this rule would have likely eliminated the first woman to win a Crown by her own hand from competing. It most certainly would have changed the story.

I continue to wonder why "opposite sex" remains the default. I wish they'd just remove all the gendered language, and say something like "If a Kingdom wishes to bar couples of the same sex from entering a Crown list, the Kingdom may apply for a waiver from the board. These waivers will be evaluated on a case by case basis." Why make equality the exception? If Kingdoms want to be discriminatory, make them step forward and make their case for it.