Often times that is to create a comfortable reading width. (https://ux.stackexchange.com/questions/108801/what-is-the-be...)

This breaks so hard with my own preferences it hard to believe it to be true, and relevant studies aren't all that convincing. The few websites I find that go to 150/200+ character lines are a blessing to read when I do. I only get to do this on my desktop on very odd sites or completely unstyled HTML pages (and there you don't get line-spacing, which is something I do want. I should probably write a script to fix that), and Hacker News, and I never want that to go away.

This wouldn't be the first thing I'm just weird about. Similarly, I find reading justified text to be just horrible, as I constantly lose track of what line I'm on. This one I believe has been debunked and raised as a genuine accessibility concern, but not all parts of the world have gotten around to recognising that. I'm also not a fan of serifed fonts, even in books. I'm not sure if there have been any studies made about that, as the serifs are supposed to be there to aid reading when printed on paper, but I consistently find a good sans-serif font to be better in all cases.

I wonder if this research is really valid. It was published 20 years ago, there is nothing in the abstract about arcdegrees and I can't read the full thing, and it's cited with zero consideration for the actual content being presented.

If Wikipedia had 70 characters per line I would never read it.

That's a good point, 2560p wasn't a popular resolution back then. I'm sure people browsing in 4k suffer worse.