[aoloe]

When you justify text for print, you almost always have to manually tweak the result to avoid wrong spacing, bad hyphenation, rivers, ... Justified text and automatic layout do not (yet) go hand in hand.

Left aligned text has also its issues but, most of the time you won't notice them on screen.

The article you're linking looks better than average, but it feels a bit too much like a text wall to my eyes... I guess that the lines contain a number of characters and words that is big enough to allow a more even distribution, at the price of longer lines that are less comfortable to read.

For me the rule is still that text that is automatically formatted should be mostly left aligned. But indeed, if you correctly setup the hyphenation, you can produce something that is somehow OK.

[Veen]

I suspect the wall-of-text effect isn’t caused by justification. Gwern is using first-line indents to signal a new paragraph instead of spacing them, as is more usual on the web.