He can't knock it himself. It was a good way to gather information and Strange used it to his advantage. Plus, he didn't mind the random appearances or conversation. He had one mirror in his trailer and it was flipped over when he didn't want company.

He gives a faint sigh to that, as if it's such a burden, "Hopefully you don't become more fragile than you normally are." It's a tease, given he has so many mirror scars all over his body. They had discussed before how he would be put back together if anything broke.

"Oh that's dirty, Mister Strange. Calling upon that to assist you in these terrible times," he sneers, looking down at him again with a snort. "I suppose it did owe you something and if it is helping you now, then so be it." Not that he's grateful. He didn't want anything to do with Creation.