Seems to have been added in this revision, slipped in with no mention in the commit message:

https://gerrit.wikimedia.org/r/#/c/125781/

-- brion

On Sun, Jun 29, 2014 at 2:50 PM, Brion Vibber <bvibber@wikimedia.org> wrote:

On Sat, Jun 28, 2014 at 6:12 PM, Jeremy Baron <jeremy@tuxmachine.com> wrote:

screenshot now uploaded instead of attached because list has a size limit:
https://i.imgur.com/oLFawll.png

[snip]

Just to report a bug - Since today, the text became blurry on the main
content area of the site while visiting wikipedia on a non-retina iPad
in portrait orientation (the top and sidebar remains sharp). You can
find a screenshot in attachment. This also happens while visiting
articles.

I can reproduce this in Safari running in the iOS 7.1 Simulator set to non-Retina iPad mode.

Looks like the blurriness is caused by or related to a CSS rule "-webkit-backface-visibility: hidden;" on body.vector-animateLayout div#content. If I toggle that off in the WebKit debugger, body text goes back to being sharp.

-- brion