For some reason, it's impossible to climb them, that's for sure. But dangerous? Jack keeps trying to climb up them and he's mostly fine. He only gets hurt because he throws himself off them.

[... it took playing a card game in which the taken damage feels real and falling off his motorcycle at the speed of 200 km/h for Crow to break his ribs, and you're saying Phoenix did that over a ledge?]

--Yeah, it's not that hard to break something. Looks like you people need to be more careful! [that coming from a notorious bone-breaker.]