I created a gadget years ago (in 2007) which places the last modified date in the small gray line under the title, having in mind, as editor, to avoid edit conflicts. It was useful when I triaged new pages, quickly seeing if some poorly formatted new page is still being edited one or two hours after its creation, so I defined 3 levels of alert: if the last modification was before 100 seconds, 8 minutes, 40 minutes (see image on the right).
It needs further research, but I think you can add points in the research it is useful also for editors for the above reason. It also append that, when I see on some random page this one was recently edited, I check if it wasn’t a vandalism and sometimes it is, so an other argument for readers and editors is: the more recent the last modification is the higher the probability of vandalism on that page is (a sort of soft "Flagged Revisions"), and even one can imagine asking the reader/editor to verify the last modification is correct and giving some alert if it is a vandalism.