Board Thread:General Discussion/@comment-22224-20180521161500/@comment-19346-20180521162744

What's the EXACT technical reason for ditching Monobook, because based on what it does I am not immediately seeing where it's doing something that 'non-compliant' (Question is prompted by potentially filing a ticket on the WMF phabricator in relation to the core Mediawiki package.)?

In any case Monobook is ancient (with a number of WMF based Mediawiki installs using the Vector skin instead.)