I do disagree with the immediate jump to mentally ill though. It's a bit of a patronising thing and extreme body mods are part of a culture and lifestyle. You can't get these things done in the UK since a big case a few years ago when a chap was sent to prison because he didn't have the correct licenses ie in surgical procedures.
Anyone with capacity has the right to make unwise decisions, even to harm themselves, otherwise there would be no addicts or alcoholics. Unwise decisions are subjective to cultural norms and fashions.
Just because someone chooses to do something you wouldn't contemplate, it doesn't necessarily make them mentally ill.