Add @references for deeply nested (3+) comments.

lms/static/coffee/src/discussion/views/response_comment_view.coffee

@@ -8,7 +8,12 @@ if Backbone?
       @$delegateElement = @$local
 
     render: ->
-      @$el.html(@template(@model.toJSON()))
+      params = @model.toJSON()
+      params['deep'] = @options.deep
+      if @options.deep
+        params['parent_id'] = @options.parent.id
+        params['parent_username'] = @options.parent.get('username')
+      @$el.html(@template(params))
       @initLocal()
       @delegateEvents()
       @renderAttrs()

lms/static/coffee/src/discussion/views/thread_response_view.coffee

@@ -27,15 +27,15 @@ if Backbone?
       MathJax.Hub.Queue ["Typeset", MathJax.Hub, element[0]]
 
     renderComments: ->
-      @model.get("comments").each @renderComment
+      @model.get("comments").each (comment) => @renderComment(comment, false, null)
 
-    renderComment: (comment) =>
+    renderComment: (comment, deep=false, parent=null) =>
       comment.set('thread', @model.get('thread'))
-      view = new ResponseCommentView(model: comment)
+      view = new ResponseCommentView(model: comment, deep: deep, parent: parent)
       view.render()
       @$el.find(".comments li:last").before(view.el)
       children = new Comments(comment.get('children'))
-      children.each @renderComment
+      children.each (child) => @renderComment child, true, comment
 
 
     toggleVote: (event) ->

lms/templates/discussion/_underscore_templates.html

@@ -95,7 +95,13 @@
 </script>
 
 <script type="text/template" id="response-comment-template">
-  <p><span class="response-body">${'<%- body %>'}</span><span class="posted-details">&ndash;posted <span class="timeago" title="${'<%- created_at %>'}">${'<%- created_at %>'}</span> by <a href="${'<%- user_url %>'}">${'<%- username %>'}</a></span></p>
+  <p id="comment_${'<%- id %>'}">
+    ${'<% if (deep) {%>'}
+    <a href="#comment_${'<%- parent_id %>'}">@${'<%- parent_username %>'}</a>:
+    ${'<% }%>'}
+    <span class="response-body">${'<%- body %>'}</span>
+    <span class="posted-details">&ndash;posted <span class="timeago" title="${'<%- created_at %>'}">${'<%- created_at %>'}</span> by <a href="${'<%- user_url %>'}">${'<%- username %>'}</a></span>
+  </p>
 </script>
 
 <script type="text/template" id="thread-list-item-template">