Thanks for the tip! I just heard about this on Twitter as well. But although this what I'm looking for, I still think it would be most reasonable to link to the source on the documentation website.
I think there's a tendency in the Racket community to rely much more on a thorough reading of manuals and docs than a peek at the source code. I personally can count on one hand the number of times I've had to look up implementation code for debugging or to figure out how to implement something. The Racket manuals, Scribble, DrRacket's integration with both, and the strong culture of documentation in user packages make for a wonderful development experience.