I was reminded of a particular anecdote I need to get out of my system.
There was a time on a particular fiction series' fan forum's IRC channel when I had to convince a very enthusiastic teenage fan that the instructions they found on 4chan to open a portal to a parallel world of that particular work of fantasy fiction was actually a method for synthesizing and inhaling poison gas.
The weird part was that they admitted they knew it was probably just a cruel prank, but were still willing to try just in case it was real. We had to actually find and link articles where the same reaction was exhibited as an actual documented suicide method, if an unreliable one at that, to convince them not to go for it.
By my estimate that person was about high school age, almost certainly over 13 and probably over 15. Mostly their behavior seemed normal for the age, certainly overenthusiastic about the fandom and with obvious signs of teenage ennui, but both of those are typical for someone in their mid-teens. It was just this strange incident of extreme gullibility and self-destructive devotion to a fandom that really stuck with me.