Look, I’m a Mac guy, and not much of a type expert, but I’m inclined to disagree. It seems to me that the absolute width and relative inverse colors of the zoomed-in example “a” were proportionate the same in the first example, whereas in the second, it was discernibly smaller in the white-on-black example. To my mind, this narrowing makes the overall readability just a smidgeon less, except in the Mint example, where I find the Firefox rendering significantly more readable.