Affects mpga branch. Confirmed in http://reading-web-staging.wmflabs.org in Firefox and Chrome.
- Visit http://reading-web-staging.wmflabs.org as an anon
- Enable previews in the footer link
- Verify previews work in the Test link at the bottom of the main page
- Visit http://reading-web-staging.wmflabs.org/wiki/Book and observe the links like ink and paper
- The links in Book show page previews
- The links in Book don't show page previews, you have to go back to the footer to enable them