In O-1, the edge chipping at Rc60 would probably not be a problem.
The concern in a sword is lateral stability - AKA breaking the blade in half with a sideways or misplaced blow. Watch Doug M. on FIF make some cuts and you will se what a misplaced blow can do to a sword ( personally, I think he is a clown).
At higher hardness, the blade will break sooner than one tempered down lower, which also increases toughness.
I do swords mainly in the mid to upper Rc50's depending on the blade type, steel, and expected use. They will all cut well at Rc56. The difference will be in how long the edge holds up in use. If the sword will only get a few demonstration cuts, and won't be chopping up Zombies daily, I would go on the safe side at Rc 56-58. IF you want it to cut tatami repeatedly at competitions and demos, go Rc 58-60.