Rich snippet (stars) on serp thanks to the plugin, but is it ok?

Hy,

first, just wanna thanks you for your lovely plugin. But, i noticed that all my pages now have stars in the middle of the title and the meta description.
I like it but i don’t understand if is it ok for google cause i red about penalty due to this. Am i wrong?

The rich snippet cause me also a lot of structured data error that i correct easily adding this code to my functions.php file:

//...
function add_mod_hatom_data($content) {
 $iso8601_date = get_the_time('c');
 $author = get_the_author();
 $title = get_the_title();
 if( is_single() || is_page() ) {
$content .= '<div class="hatom-extra"><span class="entry-title">'.$title.'</span>
ultima modifica: <span class="updated"> '.$iso8601_date.'</span> 
da <span class="author vcard"><span class="fn">'.$author.'</span></span></div>';
 }
 return $content;
 }
add_filter('the_content', 'add_mod_hatom_data');

//css hide

.hatom-extra{
display: none;
}

What do you think? Maybe i can change something?

Also testing my page on Googlepagespeed, i noticed an error due to fontawesome:

https://s25.postimg.org/dnnk6oqkf/image.png

You know maybe how can i solve this quickly?

Thanks so so so much!