It's probably one of the safest methods, if not the safest method, with regards to permanent consequences. It's incredibly hard to validate threads of people that have come on here claiming to have permanent damage, especially when compared to the multiple threads that have been posted which depict survival with very little consequence. That said, it's pretty much impossible to really understand what happens beyond the immediate, and what long-term underlying effects may be present, since the this method seems to have only really picked up in popularity quite recently. Overall, it seems lethal enough when done correctly that I don't really think there's really that much cause for concern.