Is there any support for having mobile page issues on external wikis? Honestly, this seems like something that would be beneficial to a number of wikis that are powered by MediaWiki, not just those ran by WMF.
Topic on Talk:Reading/Web/Projects/Mobile Page Issues
Well the good news is that hopefully you wont't need to do anything special for page issues on mobile! Wikimedia wikis have a history of being predominantly desktop-focused and created by numerous volunteers with various skill levels over years of development. If you have a wiki and you're wanting to follow best practices for mobile content – including notifications of issues with pages – take a look at some documentation we have that might help. Basically don't use tables for displaying information and TemplateStyles might help with mobile-targeted styling.