It won’t kill you, just check that it does not interfere with your brake pads (shouldn’t be that far up on the rim). Even if it does, it will just chew through your pads faster than normal.
Hell if I know what caused this. My theory is that this happened after my crash some weeks ago – the tire blew out right after, and the path was rough – maybe it glanced off gravel? Maybe I knocked it about while changing the tire? I remember being annoyed at first crashing and then flatting.
It’s no big deal…I’ve picked up nastier scratches than that while bounding through baby heads without negative impact on ability to brake or anything else. If it feels rough to the touch, take some emory cloth and smooth it out for the (long term) sake of your brakes.
Emery cloth is being obtained. For some reason I’d convinced myself that sanding or filing my rims is going to lead to flaming disaster, but now that I have people to blame if I die, I’m gonna try it.