Matt Watson, through his Wholesome Code brand, released a plugin called Wholesome Publishing on the WordPress plugin directory on Tuesday. Version 1.0 of the plugin adds a couple of simple but useful editing features that should help teams of writers or content designers. The plugin allows users to add nested comments on a per-block basis and mark individual blocks as drafts.
At this point, the plugin is not a fully-fledged pro editing plugin. However, its basic features go a long way toward improving collaborative publishing. It is a good first showing for a version 1.0. I hope that it continues