> I think the point the parent is making is that human vision has limited resolution.
If you can't see the difference between 4k and 1080p on a 24" monitor, then you probably need reading glasses. On a 27" monitor it's even worse. It's not so much that you can "see" the pixels, sub pixel rendering and anti-aliasing go a long way to making the actual blocky pixels go away, the difference is crisp letters versus blurry ones.
Yes, I can see the difference, but I (personally) don't notice that difference while reading. I do notice a big difference when using older monitors with lower DPI compared with 1080p on a normal-sized desk monitor, however.
If you can't see the difference between 4k and 1080p on a 24" monitor, then you probably need reading glasses. On a 27" monitor it's even worse. It's not so much that you can "see" the pixels, sub pixel rendering and anti-aliasing go a long way to making the actual blocky pixels go away, the difference is crisp letters versus blurry ones.