I think they mean to say that Cleartype (?) hurts their eyes.

It doesn't bother me tons (my eyesight, while not awful enough to mandate correction, isn't a perfect 20/20), but I can still tell when it's on, and I tend to prefer how sharp and crisp text is when it's off.  Why add extra blur when I don't have to?

Recent MacOS versions have it too, but it's more subtle and less annoying (I can still tell the difference when it's off, though).

XP had it, too, and for some reason, it wasn't so bad (maybe due to the fact that it was fully optional and off by default).  I don't recall Windows 2000 having it natively, but maybe it (or something like it) was backported, perhaps by way of an XP update?

c

Well, following the suggestion, I tried to use Windows 7 on a Kaby lake system, and Windows 7 renders everything much blurrier than Vista.

Films and texts look like over-blurred hell! Those that are going to argue, you just forgot the crispiness of Vista and even XP!

So not useful even for such simple tasks for me.

Important to note, I got a severe eye strain by just staring at the desktop! It's simply fatiguing. Watching photos via Nero 9 isn't, but looks like it bypasses the rendering to DX9, therefore they look somewhat similar to Vista's and not fatiguing.