Extreme/insane positions on everything. Not just one or two insane positions, not just political extremism; when I say everything I mean EVERYTHING. No nuance allowed. And it has to be fully sincere, otherwise you are dealing with a Jreg.
There are milder versions of this, but I have rarely met a child that didn't have a strongly held insane belief formed from their limited experiences. My favorite was a kid who told me that eating pasta supports fascism because it comes from Italy, so loving Italian products means you support Mussolini. Pizza is fine, though, because that's American.
I was a big fan of jreg pre-2020, but after giving up mainstream social media I currently believe that only cowards, frauds, and master satirists feel the need to use irony. It's arrogant to think you are the third, and I dont think Jreg is either. I think he is a coward.
I'm just glad I decided to go full moral relativism right away back then. It was a good way to speedrun maturity, although I did maintain some kooky beliefs into early adulthood such as
"if you are not multilingual you can't be a good person, and the more languages you speak the better of a person you are"
"The Democratic party is a puppet of the Republican party, and in reality the U.S. is only pretending to be a two-party state"
"The age of consent should be 25."
"Evil people can be good functioning members of society, so we shouldn't discriminate against people who hold evil beliefs as long as they are nice to others."
It was exhausting. Opposite reason from you, there was only middle ground, no black and white allowed. But it came from the same mental place. Pride, arrogance, nieveté.