The reason for this is readability. Long lines of text are empirically bad for readability, making it hard for readers to find the correct next line.

However, the line length Wikipedia picked seems to be a bad compromise. At around 120 characters per line it‘s double the recommend line length (60 characters).

If you look at newspapers, magazines and books you will see the 60 character rule of thumb adhered to pretty exactly and thoroughly. It‘s just a typographical best practice.

On the web and on wider maximized screens the issue is always the white space. Newspapers solve this issue with columns. However, that‘s not a realistic solution on the web (not so much for technical reasons, mostly because scrolling is fundamentally incompatible with columns).

> mostly because scrolling is fundamentally incompatible with columns

How so? You just scroll horizontally rather than vertically. Even actual scrolls come in both vertical and horizontal (column-based) formats.

That is actually a nice idea (and I’ve seen designers’ personal pages that do do that), but would probably look too artsy on today’s web. Gestures on mobile are also quite married to the vertical direction, so unless you’re willing to switch directions depending on screen size (way too jarring) that’s going to be somewhat broken as well.

Mouse wheels. That‘s the issue. They mostly scroll only vertically. Horizontal scrolling frequently is a massive pain for everyone involved.

> However, the line length Wikipedia picked seems to be a bad compromise. At around 120 characters per line it‘s double the recommend line length (60 characters).

Unfortunately, Wikipedia uses a lot of right-side floats, some of which are quite wide. They are also frequently referred as “on the right” in the main text, which can be quite jarring on mobile/minerva where they might be above or below.

I could imagine a breakpoint where those floats would turn into margin notes, but that sounds extraordinarily fiddly.

60 characters is way too short for comfort. Too much vertical movement makes it hard to keep track of the line I'm on. 120 is better but still too short in my opinion if the page is wide enough for longer lines.

To read one full line on [2] moving my eyes is not enough, I have to move my head. It's tiring, and when you're at the end of a line it makes it harder to come back to the beginning of the next line. Just reading a few lines on your screenshot, I ended up reading the 3rd line 2 times because my eyes went back to the wrong line, and because the lines are long I forgot the beginning of the line I just read.

So yeah I'd say [1] is strictly better for readability than [2].

> , I have to move my head.

I don't.