Index: wp-includes/formatting.php
===================================================================
--- wp-includes/formatting.php	(revision 27304)
+++ wp-includes/formatting.php	(working copy)
@@ -73,27 +73,44 @@
 		$static_characters = array_merge( array( '---', ' -- ', '--', ' - ', 'xn–', '...', '``', '\'\'', ' (tm)' ), $cockney );
 		$static_replacements = array_merge( array( $em_dash, ' ' . $em_dash . ' ', $en_dash, ' ' . $en_dash . ' ', 'xn--', '…', $opening_quote, $closing_quote, ' ™' ), $cockneyreplace );
 
+		// Pattern-based replacements of characters.
 		$dynamic = array();
-		if ( "'" != $apos ) {
-			$dynamic[ '/\'(\d\d(?:’|\')?s)/' ] = $apos . '$1'; // '99's
-			$dynamic[ '/\'(\d)/'                   ] = $apos . '$1'; // '99
-		}
+		$spaces = wp_spaces_regexp();
+
+		// '99s (apostrophe)
+		if ( "'" != $apos )
+			$dynamic[ '/\'(?=\d)/' ] = $apos;
+
+		// Single quote at start, or preceded by (, {, <, [, ", or spaces.
 		if ( "'" != $opening_single_quote )
-			$dynamic[ '/(\s|\A|[([{<]|")\'/'       ] = '$1' . $opening_single_quote; // opening single quote, even after (, {, <, [
+			$dynamic[ '/(?<=\A|[([{<"]|' . $spaces . ')\'/' ] = $opening_single_quote;
+
+		// 9" (double prime)
 		if ( '"' != $double_prime )
-			$dynamic[ '/(\d)"/'                    ] = '$1' . $double_prime; // 9" (double prime)
+			$dynamic[ '/(?<=\d)"/' ] = $double_prime;
+
+		// 9' (prime)
 		if ( "'" != $prime )
-			$dynamic[ '/(\d)\'/'                   ] = '$1' . $prime; // 9' (prime)
+			$dynamic[ '/(?<=\d)\'/' ] = $prime;
+
+		// Apostrophe in a word.  No spaces or double primes.
 		if ( "'" != $apos )
-			$dynamic[ '/(\S)\'([^\'\s])/'          ] = '$1' . $apos . '$2'; // apostrophe in a word
+			$dynamic[ '/(?<!' . $spaces . ')\'(?!\'|' . $spaces . ')/' ] = $apos;
+
+		// Double quote at start, or preceded by (, {, <, [, or spaces, and not followed by spaces.
 		if ( '"' != $opening_quote )
-			$dynamic[ '/(\s|\A|[([{<])"(?!\s)/'    ] = '$1' . $opening_quote . '$2'; // opening double quote, even after (, {, <, [
+			$dynamic[ '/(?<=\A|[([{<]|' . $spaces . ')"(?!' . $spaces . ')/' ] = $opening_quote;
+
+		// Any remaining double quotes.
 		if ( '"' != $closing_quote )
-			$dynamic[ '/"(\s|\S|\Z)/'              ] = $closing_quote . '$1'; // closing double quote
+			$dynamic[ '/"/' ] = $closing_quote;
+
+		// Single quotes followed by spaces.
 		if ( "'" != $closing_single_quote )
-			$dynamic[ '/\'([\s.]|\Z)/'             ] = $closing_single_quote . '$1'; // closing single quote
+			$dynamic[ '/\'(?=\Z|' . $spaces . ')/' ] = $closing_single_quote; 
 
-		$dynamic[ '/\b(\d+)x(\d+)\b/'              ] = '$1&#215;$2'; // 9x9 (times)
+		// 9x9 (times)
+		$dynamic[ '/\b(\d+)x(\d+)\b/' ] = '$1&#215;$2';
 
 		$dynamic_characters = array_keys( $dynamic );
 		$dynamic_replacements = array_values( $dynamic );
@@ -1865,7 +1882,7 @@
 	 */
 	$src_url = apply_filters( 'smilies_src', includes_url( "images/smilies/$img" ), $img, site_url() );
 
-	return sprintf( ' <img src="%s" alt="%s" class="wp-smiley" /> ', esc_url( $src_url ), esc_attr( $smiley ) );
+	return sprintf( '<img src="%s" alt="%s" class="wp-smiley" />', esc_url( $src_url ), esc_attr( $smiley ) );
 }
 
 /**
@@ -3781,3 +3798,24 @@
 
 	return false;
 }
+
+/**
+ * Returns the regexp for common whitespace characters.
+ *
+ * By default, spaces include new lines, tabs, nbsp entities, and the UTF-8 nbsp.
+ * This is designed to replace the PCRE \s sequence.  In ticket #22692, that
+ * sequence was found to be unreliable due to random inclusion of the A0 byte.
+ *
+ * @since 3.9.0
+ *
+ * @return string The spaces regexp.
+ */
+function wp_spaces_regexp() {
+	static $spaces;
+
+	if (empty($spaces)) {
+		$spaces = apply_filters( 'wp_spaces_regexp', '[\r\n\t ]|\xC2\xA0|&nbsp;' );
+	}
+
+	return $spaces;
+}
Index: wp-includes/functions.php
===================================================================
--- wp-includes/functions.php	(revision 27304)
+++ wp-includes/functions.php	(working copy)
@@ -2559,8 +2559,11 @@
 	 */
 	krsort($wpsmiliestrans);
 
-	$wp_smiliessearch = '/((?:\s|^)';
+	$spaces = wp_spaces_regexp();
 
+	// Begin first "subpattern"
+	$wp_smiliessearch = '/(?<=' . $spaces . '|^)';
+
 	$subchar = '';
 	foreach ( (array) $wpsmiliestrans as $smiley => $img ) {
 		$firstchar = substr($smiley, 0, 1);
@@ -2569,7 +2572,8 @@
 		// new subpattern?
 		if ($firstchar != $subchar) {
 			if ($subchar != '') {
-				$wp_smiliessearch .= ')(?=\s|$))|((?:\s|^)'; ;
+				$wp_smiliessearch .= ')(?=' . $spaces . '|$)';  // End previous "subpattern"
+				$wp_smiliessearch .= '|(?<=' . $spaces . '|^)'; // Begin another "subpattern"
 			}
 			$subchar = $firstchar;
 			$wp_smiliessearch .= preg_quote($firstchar, '/') . '(?:';
@@ -2579,7 +2583,7 @@
 		$wp_smiliessearch .= preg_quote($rest, '/');
 	}
 
-	$wp_smiliessearch .= ')(?=\s|$))/m';
+	$wp_smiliessearch .= ')(?=' . $spaces . '|$)/m';
 
 }