MathOverflow

He's likely to be the best mathematician in any room he walks into, but he wears this lightly.

He's helpful to colleagues, sporadically answering graduate students' questions on the online bulletin board Math Overflow.

He sometimes weighs in on other subjects as well, with an invariable, polite decisiveness.

When one user, exasperated by their inability to make restaurant-quality pancakes, asked for help, Pardon offered advice on how exactly to use baking powder to get the perfect consistency.