Index: src/main/java/org/apache/jackrabbit/oak/plugins/memory/ModifiedNodeState.java
===================================================================
--- src/main/java/org/apache/jackrabbit/oak/plugins/memory/ModifiedNodeState.java	(revision 1488896)
+++ src/main/java/org/apache/jackrabbit/oak/plugins/memory/ModifiedNodeState.java	(working copy)
@@ -371,8 +371,8 @@
                 return false;
             }
         }
-
-        return this.base.compareAgainstBaseState(base, new NodeStateDiff() {
+        
+        NodeStateDiff d = new NodeStateDiff() {
             @Override
             public boolean propertyAdded(PropertyState after) {
                 return properties.containsKey(after.getName())
@@ -404,7 +404,62 @@
                 return nodes.containsKey(name)
                         || diff.childNodeDeleted(name, before);
             }
-        });
+        };
+        
+        if (base instanceof ModifiedNodeState && 
+                !(this.base instanceof ModifiedNodeState)) {
+            return base.compareAgainstBaseState(this.base, new ReverseNodeStateDiff(d));
+        }
+
+        return this.base.compareAgainstBaseState(base, d);
     }
+    
+    /**
+     * A node state diff that reverses the result. It allows to write
+     * {@code a.compareAgainstBaseState(b, diff)}
+     * as
+     * {@code b.compareAgainstBaseState(a, new ReverseNodeStateDiff(diff))}
+     * , which might be more efficient depending on the implementation.
+     */
+    static class ReverseNodeStateDiff implements NodeStateDiff {
+
+        private final NodeStateDiff base;
+        
+        ReverseNodeStateDiff(NodeStateDiff base) {
+            this.base = base;
+        }
+        
+        @Override
+        public boolean propertyAdded(PropertyState after) {
+            return base.propertyDeleted(after);
+        }
+
+        @Override
+        public boolean propertyChanged(PropertyState before, PropertyState after) {
+            return base.propertyChanged(after, before);
+        }
+
+        @Override
+        public boolean propertyDeleted(PropertyState before) {
+            return base.propertyAdded(before);
+        }
+
+        @Override
+        public boolean childNodeAdded(String name, NodeState after) {
+            return base.childNodeDeleted(name, after);
+        }
+
+        @Override
+        public boolean childNodeChanged(String name, NodeState before,
+                NodeState after) {
+            return base.childNodeChanged(name, after, before);
+        }
+
+        @Override
+        public boolean childNodeDeleted(String name, NodeState before) {
+            return base.childNodeAdded(name, before);
+        }
+        
+    }
 
 }