Deploying JavaScript live to servers via Mobile.js is not the best idea, however whilst Mobile.js exists it is very easy to be tempted to do so.
No projects to my knowledge are using Mobile.js and whilst it exists it opens up a temptation to use it instead of going through a code review process.
On Friday, whilst working with the legal team I deployed some code [1] via it which looked harmless and seemed to work on various browsers but over the weekend it transpired that it had broken mediawiki.org on various iPhones and Firefox (see bug 53941).
I personally think we should kill it before we run into other problems. It is an unnecessary source of complexity in our JavaScript stack.. thoughts?
[1] https://www.mediawiki.org/w/index.php?title=MediaWiki:Mobile.js&diff=779380&oldid=776995
Version: unspecified
Severity: enhancement