Recent Comments tab

@worldinsport,

Use the CSS code below: 

#widget-comments-container.widget-comments-container a {
    line-height: 1.2;
    font-size: 13px;
}
#widget-comments-container .wpdiscuz-widget-popular-comment-author .popular-comment- 
    author-body div:first-of-type {
    font-size: 11px;
}

Put the code in the Top Admin Bar > Customize > Additional CSS > "Additional CSS" textarea, save it, delete all caches and check again. 

The red marked value can be changed as you like.  

Please don't forget to press Ctrl+F5 (twice) on the frontend before checking.