Index: src/wp-includes/formatting.php
===================================================================
--- src/wp-includes/formatting.php	(revision 28998)
+++ src/wp-includes/formatting.php	(working copy)
@@ -234,6 +234,9 @@
 				_wptexturize_pushpop_element( $curl, $no_texturize_tags_stack, $no_texturize_tags );
 			}
 
+		} elseif ( false == trim( $curl ) ) {
+			// This is a newline between delimeters.  Performance improves when we check this.
+			
 		} elseif ( '[' === $first && 1 === preg_match( '/^\[(?:[^\[\]<>]|<[^>]+>)+\]$/', $curl ) ) {
 			// This is a shortcode delimeter.