For course designers and teachers, providing at a glance a way to determine when content being used/built has been last modified in a course would be advantageous. Knowing how current the content is in a particular item provides an indicator to the course designer if the material is recent or needs updated as they determine by their pedagogical practice.

I imagine a string of text (i.e. [Last Modified: October 2, 2014 9:00 AM] ) displayed after the resource (and after any restrictive access designations).

This information would relate only to modification of settings, summaries, descriptions and content of the activity or resource itself, not to interaction within the activity by enrolled users or instructors providing feedback to students.