Yes, I've been curling. And now that I check it, the shurikens really do get thrown in the facing direction, so must be my mistake.
Maybe a bit bigger signs would be good. Here's an example of a sign - while it is possible to figure out what is written there, I didn't figure it out until I accidentally pressed the ctrl button
As for tearing there might be another reason, and those would be "subpixel" camera movements. I notice the camera shaking very slightly when I walk into obstacles, and that's when the tearing is the most likely to occur.