Just what DOES Madoka-sensei read at home, anyway? She's a closet otaku, so I suppose it's not hard to imagine.

Teachers are role models. Singing J-Rock songs and otaku hobbies aren't exactly kosher with that, hence her reaction.

So... how long before anonymous draws rule 34 on Madoka+SeikoNoOtoto (he really has no name)? ... I don't take this comic seriously AT ALL, apparently.