Index: includes/diff/DifferenceEngine.php
===================================================================
--- includes/diff/DifferenceEngine.php	(revision 56233)
+++ includes/diff/DifferenceEngine.php	(working copy)
@@ -817,8 +817,13 @@
 		$nta = explode( "\n", $wgContLang->segmentForDiff( $ntext ) );
 		$diffs = new Diff( $ota, $nta );
 		$formatter = new TableDiffFormatter();
-		return $wgContLang->unsegmentForDiff( $formatter->format( $diffs ) ) .
-		$this->debug();
+		return $wgContLang->unsegmentForDiff( $formatter->format( $diffs ) );
+## Please use proper debugging switches if you want to implement the following.
+## Be sure they are OFF by default, as they will cause systems to think output has changed when it
+## has in fact not. See bug #20601.
+## In fact why in the world is any debugging comment output carelessly left turned on by default any places in this file?
+##		return $wgContLang->unsegmentForDiff( $formatter->format( $diffs ) ) .
+##		$this->debug();
 	}
 
 	/**