Tolerable line lengths are largely determined by human biology:

* Short lines are exhausting to read because you have to move your eyes more

* Long lines are exhausting to read because you lose track of where the line is

There's no reason for this to be user defined. Just pick a reasonable line width for your given viewport and fill the remaining whitespace with useful information. Wikipedia did this very well and I genuinely do not understand why every top-level comment on HN is bashing the redesign.

Of course, the studies that you're (not) citing to back up your opinions were conducted decades ago on printed media, but never mind that. We Know Best (tm).

Ser I'm not always reading on Wikipedia, I am often skimming. Also I'm in my 40s now and I can still read long lines pretty well. Or perhaps I can still read short lines pretty poorly and I'd rather have the tradeoff of having to shift my view less often but at a longer distance.

> There's no reason for this to be user defined

I disagree because reading is just one use case. Sometimes longer lines make it easier to skim because you aren't needing to read everything, just letting your brain pattern match as you move along. In that case it can be better to fit more blocks of text in the viewport.

I believe, but cannot prove, that it's mostly because of "system justification". https://en.wikipedia.org/wiki/System_justification

As Alistair Cockburn said in his excellent post-mortem for his cohort's CASE tool efforts (paraphrasing):

People hate change.

No, seriously, people really hate change.

>There's no reason for this to be user defined

This mentality is exactly why UX designers suck. It's all about some developers forcing their weird vision on everyone with no regard for user choice even when it wouldn't cost much to include because X study claimed something.

Studies on line length are all over the place, I think the only consistent conclusions are that shorter lines (between 30-60cpl) are beneficial for readers with poor literacy skills (including non-native speakers) or for people with dyslexia or some visual disorders.

I bring this up because recent studies have managed to account for the saccade error associated with return sweeps and have found that reducing said error does not increase reading speed or comprehension.

https://link.springer.com/article/10.3758/s13414-019-01742-3

It's also worth noting that studies done on print line length aren't applicable to screen line length, and that most studies deal with lines of 30-100cpl, sometimes up to 130cpl, which isn't enough most websites rendered on a 16:9 screen or even the current Wikipedia design (on my 1080p monitor at least).