The "Bytes added" and the author information look broken when viewing a mobile difflink on the desktop site, e.g.: https://en.wikipedia.org/wiki/Special:MobileDiff/656016868 (checked in Chromium and Firefox under Ubuntu, happy to provide screenshots in case it's not reproducible elsewhere. Same diff on the mobile site.)
This is to some extent cosmetics, as (to my understanding) this special page isn't exposed systematically on desktop. But nevertheless, it exists there, and might occur in some situations such as when automatically rewriting mobile links for desktop. And on the other hand it should be easy to fix. Perhaps a good exercise for someone who wants to get their feet wet with MediaWiki CSS?
