That's not awkward at all. The comma separates "Gary Larson (no relation!)", a subordinate clause, from the main clause: "Its creator retired in 1995 […]".
Edit: As jcfields so kindly pointed out, it's apposition. Specifically, it's the use of a restrictive appositive.
To my eyes, the real awkward comma is the one after '1995'. However, The New Yorker is known to have its own, fairly specific punctuation style.