>Terrible compared to what alternatives? Showing images at half their expected size?
No, compared to showing it at the *expected* size. If my image is 800px wide, the expected size is 800px. Stretching it to 1600px mean showing it at *double* its expected size.
>On a Retina screen, images have to be scaled up somehow.
This is obviously the root of the disagreement, because I don't think that's true *at all*.
Why bother with a high density screen in the first place if you're not going to use it?
I have here a number of displays, ranging from around 100ppi to around 250ppi. Looking at the same image on the lowest and highest density displays, it looks far better on the higher one when displayed at its native size. If that gets rescaled to make it the same *physical* size, the theoretical best case scenario is that it looks like it does on the low density display, except in practice the better display means that you can really see the deficiency of the scaling.
I recognise that there is a real problem to be solved here, where some genius has specified a text height of 12px and some background image to match (or whatever), but the solution given doesn't seem like a good one at all.