This plugin provides the
last_comment sorting order which uses the modification time of their last comment to sort pages. It also updates the mtime of the page to this value.
For example, it could be useful to make active threads of discussion appear on top of the list of threads in a forum.
You'll find it in this repository, in the 'sortbylastcomment' branch:
Hi, is there a chance of seeing this plugin getting included in a release at any point soon? --sajolida