Index: wp-includes/formatting.php
===================================================================
--- wp-includes/formatting.php	(revision 25954)
+++ wp-includes/formatting.php	(working copy)
@@ -87,9 +87,9 @@
 		if ( "'" != $apos )
 			$dynamic[ '/(\S)\'([^\'\s])/'          ] = '$1' . $apos . '$2'; // apostrophe in a word
 		if ( '"' != $opening_quote )
-			$dynamic[ '/(\s|\A|[([{<])"(?!\s)/'    ] = '$1' . $opening_quote . '$2'; // opening double quote, even after (, {, <, [
+			$dynamic[ '/(?<=\A|[\s([{<]|\xC2\xA0)"(?=\S)/' ] = $opening_quote; // Any double quote at start, or preceded by space, (, {, <, [, or nbsp, and followed by a non-space.
 		if ( '"' != $closing_quote )
-			$dynamic[ '/"(\s|\S|\Z)/'              ] = $closing_quote . '$1'; // closing double quote
+			$dynamic[ '/"/'                        ] = $closing_quote; // Any remaining double quotes.
 		if ( "'" != $closing_single_quote )
 			$dynamic[ '/\'([\s.]|\Z)/'             ] = $closing_single_quote . '$1'; // closing single quote