I wonder if the writer doesn't know the characters are underage or thinks they aren't because of how they look but she should know who those characters are.
Actually most people should know.
Wtf
Oh they know....
In fact there are tons of games/books/shows/movies starring kids and teenagers that you can't really say you were unaware of unless you are reading an alternate universe story each time you go over it? Yet nevertheless people, adults, pointedly, (if you're the same age group obviously it's negligible) will playfully fantasize about them as their girlfriend/boyfriend or write smut about these characters nutting and the like (and, yes, create explicit visual renditions of them engaged in who knows what activity in devil may care contexts).
But that's another can of worms for (*checks watch*) probably a later thread in a few hours that someone will put up. :p
In all seriousness, on topic, Kotaku should collect themselves here. And mind what they are to say.... this is clearly a fair ways more delicate than free pornographic distribution of Harry Potter fan images and animation across the web that they may have forgotten is not perceived as normally by others outside the fandom might have implied!