I'm the guy who built that, and I agree. I tinkered with having another "Show Code" button at the top, but my attempts looked bulky and distracting. Still trying to figure out a better way.
As a note of feedback, I didn't notice the button at all. (Only knowing about its existence after looking at HN comments.) You do need to take a little bit a the viewer's attention for them to know about the feature.
In the meantime, pull requests quite welcome: https://github.com/jsvine/reporter