Most of that article proposes dark text light background, including the article itself being that way.
In the case of the Kindle or whatever, most devices specific to reading have highly anti-reflective surfaces, are a device in which the person can move it to the optimum distance for them from their face, and the software in those devices has parameters for resizing text. Without a highly anti-reflective surface, you will get exterior light bouncing off a black screen more because of the nature of glass/transparent material.
You’ll notice in the white text on black picture example, that the text is spaced further apart. That text would not be readable if the minimum line spacing was used.
The size of text in Cubendo, and the proximity of spacing between words/lines in some windows, is not well suited for light text on dark background.