Per User:Nick_Moyes and @TheDJ at https://www.mediawiki.org/wiki/Topic:V6nknm0p8uc8mtao people who read Wikipedia articles on their mobile devices are unable to sort tables, even when the tables are marked as sortable in the wikitext.
Here's the feature in action on desktop:
Enabling it on mobile is trivial (mw.loader.load('jquery.tablesorter'); $('.sortable').tablesorter();' ) and I'm surprised a gadget hasn't done it out of frustration of this ticket being open so long.
On mobile the code is functional, however looks a bit odd. We likely want to tweak the CSS to fully fix this issue (a small amount of work)