Did you bother to google his handle? While I don't know his pure mathematics credentials, he's nerd-famous enough to not warrant an introduction. In fact, you not recognizing it says something about you.
To be fair, we are on hacker news. I did once use on of his programs, American Fuzzy Lopper (fake advertisement lawsuit incoming if its not american). So he is not nobody apparently
What is nerd-famous supposed to be. He's at the center of some subjective in-group that exists in your head?