I got some inside info from Codepen folks about how to customize the viewer when you're giving out links.
When you use this syntax, you get JS editor on left, preview on right, and HTML/CSS hidden :)
I wonder if they plan on doing a mobile view that is less awkward.
Hang on it can be done! Full screen urls look like: http://codepen.io/carambula/full/jqlyK
Open it up in clear browser and you're in good shape. Vertical dragging still needs code to avoid scroll.