Run a view source. The code isn't what most of us consider to be best practices (table layouts and font tags all over). It could be difficult to add. But the site still works, which says something about the difference between great code and a great product. Still -- I'm with you. I wish there were a better mobile experience.
I wouldn't call Hacker News a great product, as regards the UX and layout (which is probably the worst possible way to implement a nested list in HTML.) I would call it a great community and an acceptable product. It's basically a toy that got popular because it was attached to YCombinator, and remained popular because programmers have a higher tolerance for UX pain than mere mortals.
Thanks for saying this! Then I would say, keep this style if it impacts on the quality of HN community.