i would say Reddit became mainstream in 2015 with over approximately 100 million users. That’s when I started noticing the quality of comments start going down. That’s when people stopped having discussions and started bickering more. Before that it was a lot less hostile and the topic of discussions were more fun and informative.

There was also a lot of OC at the time. You just needed to join subs in order to see it. But it was there.