Complex sentence: The Midnight Murk is an influential Wikipedia user and superhero vigilante, most known by the Wikipedia community for contributing to pages related to comic books and superheroes as well as keeping vandals and other wrongdoers in check.
Split into simpler sentences: The Midnight Murk is an influential Wikipedia user and superhero vigilante. He is most known by the Wikipedia community for contributing to pages related to comic books and superheroes as well as keeping vandals and other wrongdoers in check.