On the only occasion when my rear derailleur went where it shouldn’t have, wrecked spokes were the least of my worries. I’ve never, touch wood, had a random unprovoked gear hanger failure etc so I’ll take my chances with that. No, I was interested only in this notion that it might help keep the disc clean, but it seems not. Cassette tool out tomorrow. I need to change a tube with a too-short valve anyway. And clean my whole bike...