It's probable that HN is so feature-frozen it's not worth doing at this point, but if it were not, there are a few good reasons. The parent's example in hideStory() is a good start:
for (var i=0; i < 3; i++) { remEl($(id).nextSibling) } // pop following options row, whitespace text node, .spacer
This way, if (for instance) someone were to try to modify the layout to use margins rather than spacers, or if someone were to strip whitespace from the rendered HTML, a quick search (or manual skim of the code when something breaks) for "spacer" or "whitespace" would help someone avoid needing to step through what's being removed in Dev Tools. Minimally invasive, would greatly help someone doing code review, and doesn't even increase line count. Documenting the helper methods at the top would help newcomers to the codebase as well.
More generally, going a step further, I've been inspired in my commenting style by Jeremy Ashkenas's literate code for the Backbone library. See, for instance, http://backbonejs.org/docs/backbone.html#section-111 . The code itself is as self-explanatory as any other code I've ever seen, but the comments serve to accelerate that browsing process. Backbone, while somewhat dated nowadays, is a great level of abstraction in that the entire library can be grokked in an afternoon - but without comments, I think it would take longer. Reading time does not monotonically increase with number of characters :)
And as a third point, if there's ever something confusing enough, or you're using some infrequently-used feature of the CSS/DOM spec, such that the author or reviewer needed to look up how it worked in documentation or a forum somewhere, I encourage my team to simply add that documentation or forum link into the comments. Extremely helpful for maintainability, particularly when onboarding junior team members, allows code reviews of that line to be asynchronous whereas they would otherwise require synchronous explanation, and it's ideally just as quick to keystroke "select-url/copy/close-documentation-tab/tab-into-codebase/start-comment/paste/enter" as it is to "close-documentation-tab/tab-into-codebase."
This is Hacker News - we're the antithesis of enforced Javadoc-style comments :) But if you consider someone needing to read code without having the live input of the author, minimal comments for especially terse or creative code can quickly start to make sense, certainly in the territory of the rightmost columns of https://xkcd.com/1205/