Filter authors in Recent Comments widget

I’m running a multi-site installation with the latest version of WordPress (4.3.1), and child themes modifying a theme from Elegant Themes. Off of the main site, we run a couple of blogs, with the standard Recent Comments widget displaying the five most recent comments in the sidebars.

Here’s a link to one of the blogs on the website for illustration.

If a blog author goes in and replies to a number of comments on posts, all of the recent comments showing in the sidebar could be by only the blog author. I would prefer that the recent comments be from readers who have commented, not the blog author.

Anyone have a method for filtering out the blog authors’ names from the recent comments? I’d prefer to add something in the functions.php, rather than another plugin. Or use some other modification that won’t be overwritten in an update.

Thanks for any suggestions.
– Bill