Tats aren’t a big deal as long as they can be concealed by clothing. There are several pilots who wear long sleeved shirts for this reason. Most piercings will close up, even moderately gauged ears.
I had piercings when I was a teen, wasn’t until I began instructing that I permanently removed them. And while they closed up, there is still the telltale scar of what once was. United didn’t seem to mind....