Hi @marsm,

If you're talking about the editor font size, then you can disable it using this code in the Code Snippets plugin:

function wpforo_custom_editor_toolbar( $settings ){
   if( isset($settings['tinymce']['toolbar1']) ){
        $settings['tinymce']['toolbar1'] = 'bold,italic,underline,strikethrough,forecolor,bullist,numlist,hr,alignleft,aligncenter,alignright,alignjustify,link,unlink,blockquote,pre,wpf_spoil,undo,redo,pastetext,source_code,emoticons,fullscreen';
   }
   return $settings;
}
add_filter('wpforo_editor_settings', 'wpforo_custom_editor_toolbar', 12);