Try to disable wpDiscuz Font-Awesome Lib if your theme already loads it. You can do that in Dashboard > Comments > Settings > Styles admin page.

Just for your information. Your plugin runs an old version of font awesome so it breaks the font awesome of my whole site. This is what my theme support wrote me:

The WPDiscuz plugin is loading a different more limited version of FontAwesome, overwriting ours. You can fix that by adding the following CSS under Appearance > Customize:

.fa, .far, .fas { font-family: FontAwesome !important; }