They definitely feel like teenagers. I don't know any of them as people and they're most definitely NOT teenagers (right?). But they sure do seem like it. Then and now.
Most of the mods you see in the Smash 4 sections are most likely young (teenager probably). However, there are way older people on the staff that have been there since 2001 (when the site was initially created). Newer mods are bound to be younger if their join date was like 2012-2014. As far as I know, they were probably made a mod because their existing older mods don't want to deal (or don't deal because they're assigned to a different subforum on the site) with the Smash 4 subforums. Like, for example, you never see Mic (one of the oldest members on the staff) in the Smash 4 subforums moderating it -- I think he did at first a few times but I haven't seen him since. Then again, he's more of an admin now anyway.
I'm not sure what the qualifications are now to be a mod on there but I remember way back when it wasn't as easy to be a mod. I think things have changed because of how big the site is now compared to back when I was more active on there. With a new game on the horizon, I think AlphaZealot (the site owner) wanted more mods to keep the Smash 4 section in check from going too crazy.