Hi Stefanie,
The visibility option is added via the Jetpack plugin (or part of WordPress itself if you’re using WordPress.com). The visibility option controls where the widget is shown or hidden on your site, depending on what page you are viewing. For example, ‘show if viewing the Contact page’, or ‘hide if the current category is “Travel”‘. Unfortunately these options are not related to (and therefore don’t control) the comments displayed by our Better Recent Comments plugin.
The “show/hide if author is” option would show or hide the widget on what’s called the “author archive” page, which is a page showing all posts written by a particular author. It won’t have any effect on the comments shown in our widget unfortunately.
At the moment, there isn’t a way to achieve what you want with our plugin, but I’ll make a note of it and let you know if this feature becomes available.
Thanks for using the plugin!
Andy