They are the Seven, though... maybe quite a few of them had such gifts? I think that Janus, being a master warrior and sorcerer as he was could have been so, by training if not by nature. Frog might have had it naturally. Marle, perhaps as well, though with such weapons where one can store the energy, it's difficult to tell. Ayla as well is somewhat unclear: anyone know which way she stands, with which foot and hand forward in battle-stance? That might show it clearly, perhaps. Robo, I'd wager, is absolutely two-handed. But I'd not think it far-fetched that Crono is ambidexterous. After all, if you can use both equally, which would you use first? The one that throws the guard off the opponent and makes it more difficult for them to fight you, ie. the left. So maybe its just strategy that Crono fights with his left. Although that last little bit about not being used to the left-handed stance brings to mind the Princess Bride, for me... know what I mean?
As for the comment on the fortress building, now that you mention it, I've heard of the castle architecture as well, although I'd forgotten that.
