<p class="comment-form-comment"><textarea id="comment" name="comment" cols="45" rows="6" required>' . '</textarea></p>',

add_filter( 'comment_form_defaults', 'natali_comment_form_args' );
 
function natali_comment_form_args( $args ) {
	$req       = get_option( 'require_name_email' );
	$commenter = wp_get_current_commenter();
	$aria_req  = ( $req ? " aria-required='true'" : '' );
	$html_req  = ( $req ? " required='required'" : '' );
	$html5     = 'html5' === $args['format'];
 
	$fields    =  array(
        'author' => '<p class="comment-form-author">' . '<label for="author">'. ( $req ? '<span class="mark">*</span> ' : '' ) . __( 'Your name:', 'natali' ) . '</label><br/>' .
		            '<input id="author" name="author" type="text" value="' . esc_attr( $commenter['comment_author'] ) . '" size="50"' . $aria_req . $html_req . ' /></p>',
		'email'  => '<p class="comment-form-email"><label for="email">'. ( $req ? '<span class="mark">*</span> ' : '' ) . __( 'Your E-Mail (will not be published):', 'natali' ) . '</label><br/>' .
		            '<input id="email" name="email" ' . ( $html5 ? 'type="email"' : 'type="text"' ) . ' value="' . esc_attr(  $commenter['comment_author_email'] ) . '" size="50" aria-describedby="email-notes"' . $aria_req . $html_req  . ' /></p>',
	);
 
	$user = wp_get_current_user();
	$user_identity = $user->exists() ? $user->display_name : '';
	$post_id = get_the_ID();
	$required_text = sprintf( ' ' . __('Required fields are marked %s', 'natali'), '<span class="mark">*</span>' );
 
	$fields = apply_filters( 'comment_form_default_fields', $fields );
	$args = array(
		'fields'               => $fields,
		'comment_field'        => '<p class="comment-form-comment"><label for="comment"><span class="mark">*</span> ' . __( 'Comment:', 'natali' ) . '</label><textarea id="comment" name="comment" cols="45" rows="5" aria-describedby="form-allowed-tags" aria-required="true" required="required"></textarea></p>',
		'must_log_in'          => '<p class="must-log-in">' . sprintf( __( 'You must be <a href="%s">logged in</a> to post a comment.' ), wp_login_url( apply_filters( 'the_permalink', get_permalink( $post_id ) ) ) ) . '</p>',
		'logged_in_as'         => '<p class="logged-in-as">' . sprintf( __( 'Logged in as <a href="%1$s">%2$s</a>. <a href="%3$s" title="Log out of this account">Log out?</a>' ), get_edit_user_link(), $user_identity, wp_logout_url( apply_filters( 'the_permalink', get_permalink( $post_id ) ) ) ) . '</p>',
		'comment_notes_before' => '<p class="comment-notes">'. ( $req ? $required_text : '' ) . '</p>',
		'comment_notes_after'  => '',
		'id_form'              => 'commentform',
		'id_submit'            => 'submit',
		'class_submit'         => 'submit',
		'name_submit'          => 'submit',
		'title_reply'          => __( 'Leave a Reply' ),
		'title_reply_to'       => __( 'Leave a Reply to %s' ),
		'cancel_reply_link'    => __( 'Cancel reply' ),
		'label_submit'         => __( 'Post Comment' ),
		'submit_button'        => '<input name="%1$s" type="submit" id="%2$s" class="%3$s" value="%4$s" />',
		'submit_field'         => '<p class="form-submit">%1$s %2$s</p>',
		'format'               => 'xhtml',
	);
    return $args;
}