@Dezaki
Was it ever mentioned that there is an abundance of high quality steel ? ( not counting "magic" materials who could have any number of awesome qualities for weapon crafting )
One of the advantages of folding steel is to remove impurities and a lot of people use that as the poster child for the greatness of a katana.
But if the steel is already of great quality it can actually make it worse instead.
And yeah a Katana sacrifice durability for extra cutting power among other benefits, so hitting armor or other weapons is generally a bad idea.
But i dont think there are much of any real life swords that can actually hit a stone and NOT get fucked up real good....soo yeah...
As for armor breaking, swords are terrible weapons against armored creatures in general... you want to use spears or blunt wepons to kill a armored opponent.
Only really good thrusting swords were used against armoed units as attacking the weakpoints of the armor with trusts could penetrate it, but you can NOT cut armor in real life.
That said for killing unarmed creatures like a goblin or other beasts that don´t have armadillo armored like hides Katanas would be a great weapon.