Two features I particularly love while browsing WP are (1) Page Previews visible by hovering over wikilinks and (2) flipping through an article's images by double-clicking on one.
Unfortunately, it is not possible to use these features together. Specifically, when I am flipping through an article's pics, and read a caption with a wikilink, I cannot hover over it to preview the linked article.
Enabling previews in this environment would benefit WP readers like me who enjoy browsing the encyclopedia for the joy of learning new things.
Example: If you are logged out and view https://en.wikipedia.org/wiki/Foobar then Page Previews works on "Smokey Stover" in the image caption in the article but not in MediaViewer at https://en.wikipedia.org/wiki/Foobar#/media/File:Smokeycover.jpg.