Good story - I've heard of CTSS, it had a big influence on the guys who created Multics, which eventually spawned Unix. I seriously doubt it's a lack of commenting that prevents interpretation - I imagine a lack of hardware or other supporting functionality (missing software) is the only thing that could deter a dedicated historian-hacker. Speaking of history - here is an oldie but a goodie from the Jargon file, "The Story of Mel" - it's an epic hacker saga from the early days.
Commenting definitely isn't the only thing preventing people from running the code, but it definitely contributes to preventing people from reading it. Say, if some historian wants to learn about what the coders were thinking and why they did what they did, even technical commentary could help quite a bit, I suppose. So remember, comment for posterity!
Personally I find the notion of reading code without first running it to be meaningless[1]. We're unable to make sense of that program not because somebody didn't put some squiggles at the ends of lines prefixed by the right header, but because no muchine can run them, so we can't play with making changes and seeing what happens. [1] Cue Dijkstra rolling over in his grave.