It actually isn't a mistake so I can understand your confusion. #111 or #222 can often be used without losing readability but this doesn't mean black is a mistake. When's the last time you went to a website and said "This text is just too dark!". Hopefully I don't come off too rude, the idea that black as a text color is a mistake is almost offensive to me. Different perspectives.

Well, there are plenty of studies that show high contrast makes for readability issues. For example, I get faint after-images that flick around the page when reading black text on white. It's very distracting.

I get your point about different perspectives, but for web pages we want everyone to read, we should be designing for the lowest common denominator.

Using #111 or #222 softens the page a tad without making it harder to read.

Hypocritically, the text on this article's page is black.

Great catch. Although, in my defense I'm always looking to save time so I just used out of the box settings on the wordpress "Platform" theme. If you're starting from scratch on your own site, dont make this mistake :)

One reason I avoid using pure black or pure white these days is I blend text towards whatever is behind it. Text tends to look a lot heavier on the screen than it does in Photoshop (especially if the designer likes to use lighter font weights which generally don't work for the web), and you can really mitigate how heavy the text feels, and reduce the contrast (which mimicks the superior rasterisation going on in Photoshop) by moving the color of the text towards the colour of its background. If you have black text on brown, make the black text slightly brown, for example.