http://www.paulund.co.uk/disable-emojicons-introduced-in-wordpress-4-2

remove-emoji.php

function pw_remove_emojicons() 
{
    // Remove from comment feed and RSS
    remove_filter( 'the_content_feed', 'wp_staticize_emoji' );
    remove_filter( 'comment_text_rss', 'wp_staticize_emoji' );

    // Remove from emails
    remove_filter( 'wp_mail', 'wp_staticize_emoji_for_email' );

    // Remove from head tag
    remove_action( 'wp_head', 'print_emoji_detection_script', 7 );

    // Remove from print related styling
    remove_action( 'wp_print_styles', 'print_emoji_styles' );

    // Remove from admin area
    remove_action( 'admin_print_scripts', 'print_emoji_detection_script' );
    remove_action( 'admin_print_styles', 'print_emoji_styles' );
}
add_action( 'init', 'pw_remove_emojicons' );