I think the main danger of starting too young, at least for me anyway, is the over-eagerness to gain, spending less time on warmups and kegels and more time on manual stretching and jelqing. These days I wonder if my penis would have grown a bit more naturally if I hadn’t began PE at 16. Sure, you could have damaged your penis, but when it comes down to it, a penis is a penis, and whether you start at 16 or 26, the difference can’t be that drastic. Lifting weights at 16 doesn’t “damage” your muscles, and I think PE and bodybuilding ARE very comparable, regardless of what anybody says.