You're actually right about maximum contrast, but wrong about that meaning maximum readability (the two things don't go hand in hand even though one might think they do). Solid black versus solid white reads well, but is more tiring on the eyes than something lighter on solid white (which is what the author is doing by using dark grey), particularly for long passages of text.
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I like that layout, its readable. But why not make the default text-color #000 instead of #444 for maximum contrast and readability?
You're actually right about maximum contrast, but wrong about that meaning maximum readability (the two things don't go hand in hand even though one might think they do). Solid black versus solid white reads well, but is more tiring on the eyes than something lighter on solid white (which is what the author is doing by using dark grey), particularly for long passages of text.