This "blame" function would be similar to the one which already exists on GitHub (i.e. https://github.com/wikimedia/mediawiki/blame/master/mw-config/index.php).

This function would be helpful for different users to see which users edited which parts of a page, without having to search through all the revisions to find when it was changed (which can be a lot depending on the page).

If anyone is interested an extension should be created for this purpose, or maybe even integrated into core.