Can I disable the linear image scaling in Safari on a retina display? I have two MacBook Pros: one with Retina, and one without. Although browsing the web with Retina has much sharper text, most images appear noticeably blurry.

For websites that have not put in the effort to have Retina optimized images, I'd much rather their images appear pixelated than blurry. Can I tell Safari to use nearest-neighbour scaling?
What you want to do is force the image-rendering CSS property to be set to optimizeSpeed (see here). You could use the Stylish browser extension to achieve this.

Create a new custom style:

* {
image-rendering: optimizeSpeed !important;
}


Set "Apply to" to "Global".