Board Thread:General Discussion/@comment-24096104-20151027195850/@comment-4731443-20151027205940

See User_blog:Kirkburn/Technical_Update:_October_26,_2015: "The special syntax highlighted editor currently used on portable infobox pages will be rolled out to all template pages, to give a consistent user experience. The existing user preference to disable syntax highlighting will turn this off." (emphasis mine)