Index: wp-includes/functions-formatting.php
===================================================================
--- wp-includes/functions-formatting.php	(revision 2576)
+++ wp-includes/functions-formatting.php	(working copy)
@@ -12,6 +12,7 @@
 			$curl = str_replace('---', '—', $curl);
 			$curl = preg_replace('/(\s)--(\s)/', '$1—$2', $curl);
 			$curl = str_replace('--', '–', $curl);
+			$curl = str_replace('xn–', 'xn--', $curl);
 			$curl = str_replace('...', '…', $curl);
 			$curl = str_replace('``', '“', $curl);