> Pure black looks unnatural on a screen, and pure white is too bright.
Your screen does not reproduce pure black or white. Contrast ratios on LCD displays are already bad enough. No need to make it worse. People have contrast and brightness controls on their displays. Stop making comfort decisions for them. Let the user choose for themselves.
> Your screen does not reproduce pure black or white
The black on my screen is darker than the darkest dark in my environment, and the white is brighter than looking right into my ceiling lamp.
For all intents and purposes, it does reproduce pure black and white.
For readability, the contrast range should be clamped to that of paper – pure black ink on white paper looks the same as using #444444 on #eeeeee on my (calibrated) monitor.
To compensate for people with misconfigured monitors, extending the range to the colors mentioned in the article makes sense, but not any further, as that's going to be painful to look at.
Please properly configure your monitor instead. To be able to accurately represent images, the contrast of #000000 to #ffffff needs to be much larger than the contrast of any text in any reasonable situation.
And before I get the suggestion "just change your screens configuration to only reproduce colors visible on paper":
It's useful to be able to reproduce colors far beyond the range of print. Not everything IRL is colored by reflective pigments. From sunsets to iridescent birds, there's lots of colors and contrast ranges available in real life that your screen should accurately produce as well.
Your screen does not reproduce pure black or white. Contrast ratios on LCD displays are already bad enough. No need to make it worse. People have contrast and brightness controls on their displays. Stop making comfort decisions for them. Let the user choose for themselves.