Hi @berndg,
Below is the selector you should use:
#wpcomm .wc-comment-right .wc-comment-text .wpfcp-comment-info a{/* here should be added your custom CSS rules */}
For example, if you'd like to change the font-size and background-color you should use the following code:
#wpcomm .wc-comment-right .wc-comment-text .wpfcp-comment-info a{
font-size: 20px !important;
background-color: red !important;
}
The CSS code should be added in Top Black Admin Bar > Customize > Additional CSS, delete all caches
and press Ctrl+F5 (twice) on that page.
Note: You can change the red mark value.