Paintball was fun but can lead to scarring. I got a scar on my bicep from one, it finally faded 10 years later and another one, my 2nd time playing.
I covered up much better but got hit on the finger and received a ball-shaped scar (it also faded since then). I don't think it's common but possible if you have thin skin.
That being said, I don't think it's a great idea to increase the pressure on the gun.
I've had airsoft rounds get literally stuck in my arm before to the point where I had to pry them out (which absolutely left me with scars).
I'd actually never heard of anyone getting scars from paintball- something I always attributed to their greater surface area on impact. I guess I'm not surprised but I am glad the 100+ paintball hits I took never left a serious mark.
I played paintball only once and managed to get shot square in the throat. It didn't leave a scar, but it did bleed a little bit, and freaked me out a lot at the time—for a few minutes anyway.
I've also experienced getting nailed in the throat with a paintball, and for a real brief time I got worried that it damaged my windpipe. The other most painful hit I took was right in the "webbed" part on the hand in between fingers - my hand locked up in pain!
I covered up much better but got hit on the finger and received a ball-shaped scar (it also faded since then). I don't think it's common but possible if you have thin skin.
That being said, I don't think it's a great idea to increase the pressure on the gun.