diff --git a/source/java/org/alfresco/repo/forum/CommentService.java b/source/java/org/alfresco/repo/forum/CommentService.java
index 73e8b6c0e4..a673e911bf 100644
--- a/source/java/org/alfresco/repo/forum/CommentService.java
+++ b/source/java/org/alfresco/repo/forum/CommentService.java
@@ -38,12 +38,10 @@ public interface CommentService
      * {@link ForumModel#ASPECT_DISCUSSABLE fm:discussable} aspect.
      * 
      * @param descendantNodeRef The nodeRef which descends from the f:discussable node.
-     * @param expectedNodeType if not <tt>null</tt>, this is an assertion by calling code that the descendantNodeRef
-     *                           is of the specified type.
      * @return the fm:discussable ancestor if there is one, else <tt>null</tt>
      * @throws AlfrescoRuntimeException if the specified expectedNodeType is not correct.
      */
-    NodeRef getDiscussableAncestor(NodeRef descendantNodeRef, QName expectedNodeType);
+    NodeRef getDiscussableAncestor(NodeRef descendantNodeRef);
     
     /**
      * This method retrieves the {@link ForumModel#TYPE_TOPIC fm:topic} NodeRef which holds the Share comments for
diff --git a/source/java/org/alfresco/repo/forum/CommentServiceImpl.java b/source/java/org/alfresco/repo/forum/CommentServiceImpl.java
index 78a1a67ca9..491cd1247f 100644
--- a/source/java/org/alfresco/repo/forum/CommentServiceImpl.java
+++ b/source/java/org/alfresco/repo/forum/CommentServiceImpl.java
@@ -49,27 +49,38 @@ public class CommentServiceImpl implements CommentService
     }
     
     @Override
-    public NodeRef getDiscussableAncestor(NodeRef descendantNodeRef, QName expectedNodeType)
+    public NodeRef getDiscussableAncestor(NodeRef descendantNodeRef)
     {
-        final QName actualNodeType = nodeService.getType(descendantNodeRef);
-        if (expectedNodeType != null && !actualNodeType.equals(expectedNodeType))
-        {
-            StringBuilder msg = new StringBuilder();
-            msg.append("Node ").append(descendantNodeRef)
-               .append(" is of type ").append(actualNodeType)
-               .append(", not ").append(expectedNodeType);
-            throw new AlfrescoRuntimeException(msg.toString());
-        }
+        // For "Share comments" i.e. fm:post nodes created via the Share commenting UI, the containment structure is as follows:
+        // fm:discussable
+        //    - fm:forum
+        //        - fm:topic
+        //            - fm:post
+        // For other fm:post nodes the ancestor structure may be slightly different. (cf. Share discussions, which don't have 'forum')
+        //
+        // In order to ensure that we only return the discussable ancestor relevant to Share comments, we'll climb the
+        // containment tree in a controlled manner.
+        // We could navigate up looking for the first fm:discussable ancestor, but that might not find the correct node - it could,
+        // for example, find a parent folder which was discussable.
         
         NodeRef result = null;
-        for (ChildAssociationRef parentAssoc = nodeService.getPrimaryParent(descendantNodeRef);
-             parentAssoc != null && parentAssoc.getParentRef() != null;
-             parentAssoc = nodeService.getPrimaryParent(parentAssoc.getParentRef()))
+        if (nodeService.getType(descendantNodeRef).equals(ForumModel.TYPE_POST))
         {
-            if (nodeService.hasAspect(parentAssoc.getParentRef(), ForumModel.ASPECT_DISCUSSABLE))
+            NodeRef topicNode = nodeService.getPrimaryParent(descendantNodeRef).getParentRef();
+            
+            if (nodeService.getType(topicNode).equals(ForumModel.TYPE_TOPIC))
             {
-                result = parentAssoc.getParentRef();
-                break;
+                NodeRef forumNode = nodeService.getPrimaryParent(topicNode).getParentRef();
+                
+                if (nodeService.getType(forumNode).equals(ForumModel.TYPE_FORUM))
+                {
+                    NodeRef discussableNode = nodeService.getPrimaryParent(forumNode).getParentRef();
+                    
+                    if (nodeService.hasAspect(discussableNode, ForumModel.ASPECT_DISCUSSABLE))
+                    {
+                        result = discussableNode;
+                    }
+                }
             }
         }
         
diff --git a/source/java/org/alfresco/repo/forum/ForumPostBehaviours.java b/source/java/org/alfresco/repo/forum/ForumPostBehaviours.java
index b95ff12e35..10d8179d05 100644
--- a/source/java/org/alfresco/repo/forum/ForumPostBehaviours.java
+++ b/source/java/org/alfresco/repo/forum/ForumPostBehaviours.java
@@ -196,7 +196,7 @@ public class ForumPostBehaviours implements NodeServicePolicies.OnCreateNodePoli
     {
         // We have a new or a deleted comment under a discussable node.
         // We need to find the fm:commentsCount ancestor to this comment node and adjust its commentCount
-        NodeRef discussableAncestor = commentService.getDiscussableAncestor(fmPostNode, ForumModel.TYPE_POST);
+        NodeRef discussableAncestor = commentService.getDiscussableAncestor(fmPostNode);
         
         if (discussableAncestor != null)
         {