How to replace native comment_count with Comments Evolved aggregate count

Few issues here.

• use add_filter() instead of apply_filters(), to register your custom callback.

• return the value within your filter’s callback.

• use the get_comments_number filter instead of the comments_number filter, since you only want to change the number and not the whole output of the comments_number() function.

• prefix the name of your custom callbacks, to avoid possible name collisions.

So try this version instead:

function wpse_comments_evolved_number( $count ) 
{
    // Override the comment count
    if( function_exists( 'comments_evolved_get_total_count' ) )
        $count = comments_evolved_get_total_count();

    // We must then return the value:
    return $count;
}
add_filter( 'get_comments_number', 'wpse_comments_evolved_number');

where we make sure the function comments_evolved_get_total_count() exists. We don’t want to bring down the whole site, if that plugin is uninstalled.

Hope it works.