I can think of a few distinct qualities that become a redditor;
Inauthenticity
Entitlement
Being a total wimp in both the physical and mental sensibilities
Contriving and/or carefully Tailoring beliefs, statements, and personality in a way most likely to guarantee "upvotes" from other users
Giving any amount of a shit about how other people react to what is said or done, caring about things like "upvotes"
Social Awkwardness, having an aura of Patheticry
Following all of the embarrassing trends and micropropagandas that globohomo regularly feeds to the public (redditors LOVE repeating things, like a parrot. They love nothing more in this world than repeating a "fact.")
Being completely unable to comprehend, respect, or emotionally cope with other people's opinions
Wasting time by engaging in provocative arguments that hold no comedic value and serve only to be a platform to bitch and moan like a woman
Inability to laugh at oneself and take people making fun in stride; reacting to these kinds of shitposts and nonsense by initiating gay little arguments and whine like a gay little idiot
Extreme Pettiness
Tattling
etc.etc.
This doesn't mean anyone who has these traits is a redditor, but every redditor has these traits.