When I was a kid, my relatives would joke about piercing my ears because I have huge earlobes. Since then, I have lived by the rule “no body modifications without superpowers.” Maybe it is just my avoidance of permanent changes to my body, but I am not willing to get a tattoo or piercing without gaining some sort of superpower in return, like X-Men‘s Ink.
As much as I love Batman now, who knows how I will feel about him when I turn seventy. Or how my hands will look by then. Or how everyone who I shake hands with may feel about Batman. Getting a tattoo or piercing also means I cannot donate blood for at least a year.
If I do really become Batman, tattoos and piercings would make me more easily identifiable. Also, piercings would probably be uncomfortable under a tight costume, or an easy target in a fight if exposed. And even if they really did give me superpowers, it would be selling out the ideal of Batman being the ultimate badass normal.
But that does not mean I am opposed to body mods on others.