For many people, high intensity/high contrast also causes eyestrain. There's nothing wrong or unreadable about medium contrast text, despite what the somewhat triumphalist contrastrebellion would have you believe.
I hate that, personally. I don't always have to agree with whoever downvoted, or sometimes I'm just curious about what it said.
Especially the lowest contrast, after several downvotes, that's just stupid, because it's pretty much unreadable unless you select the text. So you know there's text, but you can't really read it, then why show it at all?
Except that's not a downvoted comment or an old version as far as I can tell; it's the text of a Ask HN/Show HN thing. I never really understood why those are colored gray, either.
In some agreement... According to an article on "color for developers" that was posted at some point on HN, one gets a better "pop" contrast if there is a smidgeon of color. As I read it, using white or black, regardless of the other color involved in the combo, is less effective. One should strive instead to add at least a little bit of color and contrast that color with the other. For example, if you toss a tiny bit of blue into your black, then you should toss a tiny bit of yellow/orange into your white. The contrast is not in symmetric values either; R, G, and B have different contributions to the brightness.
If I have the time to dig up the article I am thinking about, I will add it to this post.