This is interesting to me (I'm also a PhD student with research interests related to privacy and anonymity). Yesterday I was thinking something similar about the distinction, in terms of negative mental health effects, between places like HN where most of us are pseudonymous (if not anonymous) and places like Facebook, Instagram, etc. where your real persona is more of a factor and is usually tied to real photos of yourself, your friends, your home, etc. Like you, I also grew up on pseudonymous forums starting around age 12. I've always found forums like this to be somewhat addictive, but I think not nearly as addictive as Facebook and Instagram are for many people. I think it helps that I don't suffer in-real-life social consequences for what "warner25" writes on here, nor for who does and doesn't see it, and I could easily abandon this pseudonym tomorrow. So maybe that's healthier?

I'm just struggling with the idea because it runs counter to a couple other ideas: First, that social networking with people you actually know is the good part while broadcasting to the world through social media to collect likes and followers is the bad part. Second, that anonymity and pseudonymity bring out the most toxic behavior in people, so things like "real name" policies are better.