User blog comment:Rupert Giles/Layout Changes: Breakpoints and Typography/@comment-1820055-20150525002215/@comment-452-20150527185111

As has been said many many times throughout the comments: It is aimed at anyone with less than Desktop XL width, due to the fact that (apparently) some Desktop XL users were formatting tables/templates/articles to only look good at high resolutions.

I say "apparently" because I haven't actually seen these wide-formatted articles, since no-one who claims their articles are "ruined" has posted a screenshot or even a link to back up their claims. The only links and screenshots which have been posted have been regarding the actual bugs which Wikia has acknowledged were not intended.