Well, since every new chapter must bring us a new thread, I am taking the liberty to create this one. I've not seen chapter 416 yet, since I'm at work and can't download the chapter here, but a lot of comments in the threads seem to boubt Zoro's ability to cut steel. So, let's discuss this here!
In my opinion, I think Zoro can cut anything, but it is not a simple math of "if he can cut steel, then he can always cut steel. Just look at what Zoro began to cut after his fight with Mr. 1.
After that fight, Zoro did greater and greater impossible feats. Look at what he has done at the sea train, or the damage he caused at the gates of the Coutrhouse in EL, for example. Those are impossible feats, but he can do that because those are inanimate objects. No matter if they are steel or not, he can cut then, because he is strong enough to overcome an inanimate thing.
However, things are not so easy when the object he tries to cut is infused with the spirit of its wielder. That's why Zoro can cut the huge gates of the courthouse, but couldn't simply cut Kaku's swords in their earlier fight.
Confused?
Remember the Mr. 1 fight. When Zoro was walking the fine line between life and death and hear the breath of things, he "infused his spirit into his sword" and then could not cut a leaf, but then cut through rock. Does it matter if it was rock or steel? At that moment, it did not matter, because Zoro's spirit was strong enough to cut it.
However, he can't cut Kaku's (or in the future, Mihawk's) swords so easily, because by holding their swords, the battle is not about steel against steel, but spirit against spirit.
I see a lot of people around here commenting that Zoro can cut things based on their hardness. And I also see comments of people "disappointed" because Zoro can't cut Kaku's nose. Don't be disappointed: it is not that Zoro can't cut Kaku's nose, it is that Zoro must overcome Kaku's strength (and thus become stronger) in order to cut him.
What do you think?