A nice feature of the Extra Theme is its integrated post ratings system. Users can easily rate posts (on a 5-star scale). The average rating for posts is then displayed in various places, and can be used to sort the posts by popularity. While it is possible to selectively disable ratings for particular posts there is not, to my knowledge, an option to completely disable ratings throughout the entire site.

To disable post ratings globally, we can add the following into functions.php (ideally into the functions.php file of a child theme):

/* Disable star ratings */
function disable_ratings() { return false; }
add_filter('extra_is_post_rating_enabled', 'disable_ratings');

(Note that editing .php files can be risky, so be sure to make a backup of your site files before adding this code.)

Now you should find that users no longer have the option to rate posts, and that the post ratings are not displayed in post listings, etc.