I think teens do it to feel edgy.
I'm not saying that's the ONLY reason they do it, but they hear about it and see others doing it and it's a case of monkey see, monkey do.
Who is 'him'? When I click the link it goes to Twitter and asks me to log in. I can't tell who you are taking about.
Yeah kind of. A lot of duplicate material. But that's to be expected I guess. The ratio of tech to non tech stuff is too high, and I hate memes but that's just personal preference.
I just browse 'all' on my local instance every once in a while to see if any new interesting communities have appeared, and then I'll subscribe to them and go back to just browsing 'subscribed'.
I figure eventually I'll discover the best communities that I'm interested in but I'm not expecting it to happen overnight.