Index: wp-includes/comment-template.php
===================================================================
--- wp-includes/comment-template.php	(revision 23618)
+++ wp-includes/comment-template.php	(working copy)
@@ -1518,15 +1518,16 @@
 	$user = wp_get_current_user();
 	$user_identity = $user->exists() ? $user->display_name : '';
 
-	$req = get_option( 'require_name_email' );
+	$req      = get_option( 'require_name_email' );
 	$aria_req = ( $req ? " aria-required='true'" : '' );
-	$fields =  array(
+	$html5    = isset( $args['format'] ) && 'html5' === $args['format'];
+	$fields   =  array(
 		'author' => '<p class="comment-form-author">' . '<label for="author">' . __( 'Name' ) . ( $req ? ' <span class="required">*</span>' : '' ) . '</label> ' .
 		            '<input id="author" name="author" type="text" value="' . esc_attr( $commenter['comment_author'] ) . '" size="30"' . $aria_req . ' /></p>',
 		'email'  => '<p class="comment-form-email"><label for="email">' . __( 'Email' ) . ( $req ? ' <span class="required">*</span>' : '' ) . '</label> ' .
-		            '<input id="email" name="email" type="text" value="' . esc_attr(  $commenter['comment_author_email'] ) . '" size="30"' . $aria_req . ' /></p>',
+		            '<input id="email" name="email" type="' . ( $html5 ? 'email' : 'text' ) . '" value="' . esc_attr(  $commenter['comment_author_email'] ) . '" size="30"' . $aria_req . ' /></p>',
 		'url'    => '<p class="comment-form-url"><label for="url">' . __( 'Website' ) . '</label>' .
-		            '<input id="url" name="url" type="text" value="' . esc_attr( $commenter['comment_author_url'] ) . '" size="30" /></p>',
+		            '<input id="url" name="url" type="' . ( $html5 ? 'url' : 'text' ) . '" value="' . esc_attr( $commenter['comment_author_url'] ) . '" size="30" /></p>',
 	);
 
 	$required_text = sprintf( ' ' . __('Required fields are marked %s'), '<span class="required">*</span>' );
@@ -1543,6 +1544,7 @@
 		'title_reply_to'       => __( 'Leave a Reply to %s' ),
 		'cancel_reply_link'    => __( 'Cancel reply' ),
 		'label_submit'         => __( 'Post Comment' ),
+		'format'               => '',
 	);
 
 	$args = wp_parse_args( $args, apply_filters( 'comment_form_defaults', $defaults ) );
@@ -1556,7 +1558,7 @@
 					<?php echo $args['must_log_in']; ?>
 					<?php do_action( 'comment_form_must_log_in_after' ); ?>
 				<?php else : ?>
-					<form action="<?php echo site_url( '/wp-comments-post.php' ); ?>" method="post" id="<?php echo esc_attr( $args['id_form'] ); ?>">
+					<form action="<?php echo site_url( '/wp-comments-post.php' ); ?>" method="post" id="<?php echo esc_attr( $args['id_form'] ); ?>"<?php echo $html5 ? ' novalidate' : ''; ?>>
 						<?php do_action( 'comment_form_top' ); ?>
 						<?php if ( is_user_logged_in() ) : ?>
 							<?php echo apply_filters( 'comment_form_logged_in', $args['logged_in_as'], $commenter, $user_identity ); ?>