User blog comment:Cs2maor/SO ... do you like zoro's new scar ?/@comment-266457-20111009155108

It might also be that he CAN open his eye, just only does so in serious battles. Pretty much the opening of his left eye becomes his new put-on-bandana. A sign that from that moment he will be completely serious in taking the enemy out. Pretty much you can call it: "an eye for battle" which means it's an eye he trains specifically for battles and thus in time of peace never opens it (since it defeats the purpose).

And yes, I prefer him with 1 eye, somehow sword-users seem more awesome with 1 eye instead of 2.