Some websites include tags with underscore () and dashes (-) like so: fishingnets, big-bus.

As of CommentPiG 2.1.6

[+] Support for dash-spaced & underscore-spaced tags – Instead of
supporting only standard tags (e.g. “hello world”) for comment
targeting, the plugin can now handle the two additional tag spacing
types – dash and underscore, e.g. “hello-world” and “hello_world”.