Index: includes/diff/DifferenceInterface.php
===================================================================
--- includes/diff/DifferenceInterface.php	(revision 68310)
+++ includes/diff/DifferenceInterface.php	(working copy)
@@ -790,10 +790,19 @@
 		}
 
 		$n = $this->mTitle->countRevisionsBetween( $oldid, $newid );
-		if ( !$n )
-		return '';
-
-		return wfMsgExt( 'diff-multi', array( 'parseinline' ), $n );
+		if ( !$n ) {
+			return '';
+		} else {
+			$dbr = wfGetDB( DB_SLAVE );
+			$res = $dbr->select( 'revision', 'DISTINCT rev_user_text',
+				array(
+					'rev_page = ' . $this->mOldRev->getPage(),
+					'rev_id > ' . $this->mOldRev->getId(),
+					'rev_id < ' . $this->mNewRev->getId()
+				), __METHOD__
+			);
+			return wfMsgExt( 'diff-multi', array( 'parseinline' ), $n, $dbr->numRows( $res ) );
+		}
 	}
 
 
Index: languages/messages/MessagesEn.php
===================================================================
--- languages/messages/MessagesEn.php	(revision 68310)
+++ languages/messages/MessagesEn.php	(working copy)
@@ -1613,7 +1613,7 @@
 'compareselectedversions'  => 'Compare selected revisions',
 'showhideselectedversions' => 'Show/hide selected revisions',
 'editundo'                 => 'undo',
-'diff-multi'               => '({{PLURAL:$1|One intermediate revision|$1 intermediate revisions}} not shown)',
+'diff-multi'               => '({{PLURAL:$1|One intermediate revision|$1 intermediate revisions}} by {{PLURAL:$2|one user|$2 users}} not shown)',
 
 # Search results
 'search-summary'                   => '', # do not translate or duplicate this message to other languages