I wonder why, then, HN comments don't adhere to that: .comment { max-width:1215px } in news.css here on my system, which feels very readable and reasonable at around 200 chr per line at 100% scaling. I also disagree with the 70 chr recommendation: with this article, literally the entire body is limited to a very small max width which takes up between a quarter to a third of the screen on two different computers I use at home. It's a distractingly bad experience to read, so much so that I went in and modified that CSS rule just to get through it. 1200 felt right and made it a much more visually pleasing square, rather than a thin column in a sea of stark gray.

There are actual standards for this, but they're more like recommendations, and ironically https://www.w3.org/TR/UNDERSTANDING-WCAG20/visual-audio-cont... recommends "Width is no more than 80 characters or glyphs (40 if CJK)." while the first line of the paragraph explaining why is 112 characters wide and looks pretty much fine / comfortable to read on my screens.

While there are psychological reasons to use shorter line lengths, as this SO answer details the whole 80 column width thing goes all the way back to punchcards in 1928 https://softwareengineering.stackexchange.com/questions/1486...

Edit: here's what HN comments would look like with 65-70chr per line: https://i.imgur.com/yeMF6IY.png vs default with 1215px per the news.css rule: https://i.imgur.com/IXNyhfL.png .