Holy shit. I remembered the original comic, but didn't remember what the subject matter of it was. So if you hadn't left this comment, I would have just gone on believing that the OP's version was Randall's version.
Yeah, I've seen people riff on xkcd comics before but they usually do a bad job of matching the handwriting/font (I don't know if Randall hand-letters these or if he types in a handwritey font). It's often a deliberately bad job, because indicating that they are changing the original is a part of the message/artistic expression. Like when a word is covered with a black bar with white letters in it in a different font, an obvious revision, it's like hearing a different voice interrupt.
There was that one comic that Randall did (Lorenz) where you could choose one of several paths and write your own text in the last panel. In order to implement that Randall had to create a font of his own handwriting. I wouldn't be surprised if OP just ripped the .woff file or similar.