That was me, apparently much to the dislike of a number of HNers :)
Thank you very much for the pointer to the notebook although it is not easy to access, you seem to need a Wolfram account to get to it.
[EDIT]: "Sorry, you do not have permission to access this item." after I logged into Wolfram ...
> Since it isn’t really useful for practical computation, I didn’t think code would be useful
This is a very common misconception.
There is a large category of people out there (software engineers among other) that find it much easier to read code than reading abstract math formulas full of weird greek letters and which typically pre-suppose what the reader does and doesn't know (things that are considered "trivial" by the author and not worth mentioning in the paper is often a huge obstacle for the reader to proceed with understanding what goes on).
Code is explicit to the degree that a machine can execute it, and therefore often way easier as a path to understanding an idea.
Publishing code also has the minor benefits of actually exposing things that are claimed to work but often don't - again because a machine can execute it whereas a math formula in a PDF does not have that nice property.