Use placeholders in comment form

/**
 * Change the comment area text
 *
 * @since  1.0.0
 * @param  array $args
 * @return array
 */
function ea_comment_text( $args ) {
    $args['comment_field'] = str_replace( 'textarea', 'textarea placeholder="Enter your message here"', $args['comment_field'] );
    $args['fields']['author'] = str_replace( 'input', 'input placeholder="Your Name"', $args['fields']['author'] );
    $args['fields']['email']  = str_replace( 'input', 'input placeholder="Your Email"', $args['fields']['email'] );
    $args['fields']['url']    = str_replace( 'input', 'input placeholder="Your Website"', $args['fields']['url'] );
	return $args;
}
add_filter( 'comment_form_defaults', 'ea_comment_text' );