So, I searched the forums and I may have missed it but how does one usually tell when a fic is written and posted by someone who is underage.

I remember how I wrote before I turned 18, how I wrote about sex, violence, cursing, ect it's censored, sometimes unintentionally but I mean I had a hard time typing out sex organs! I feel like sometimes I read stories that could have been written by a younger me.

Whats the protocol for this? How do you tell if their bio doesn't specifically say they're underage? I feel like this is a gray area.