Show current following status in list view.

lms/static/coffee/src/discussion/content.coffee

@@ -421,6 +421,12 @@ if Backbone?
       @set('thread', @)
       super()
 
+    follow: ->
+      @trigger "thread:follow"
+
+    unfollow: ->
+      @trigger "thread:unfollow"
+
   class @ThreadView extends @ContentView
 
   class @Comment extends @Content

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

@@ -44,8 +44,10 @@ class @DiscussionThreadView extends Backbone.View
     @$(".dogear").toggleClass("is-followed")
     url = null
     if @$(".dogear").hasClass("is-followed")
+      @model.follow()
       url = @model.urlFor("follow")
     else
+      @model.unfollow()
       url = @model.urlFor("unfollow")
     DiscussionUtil.safeAjax
       $elem: $elem

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

@@ -5,11 +5,17 @@ class @ThreadListItemView extends Backbone.View
     "click a": "threadSelected"
   initialize: ->
     @model.on "change", @render
+    @model.on "thread:follow", @follow
+    @model.on "thread:unfollow", @unfollow
   render: =>
     @$el.html(@template(@model.toJSON()))
     if window.user.following(@model)
-      @$("a").addClass("followed")
+      @follow()
     @
   threadSelected: ->
     @trigger("thread:selected", @model.id)
     false
+  follow: =>
+    @$("a").addClass("followed")
+  unfollow: =>
+    @$("a").removeClass("followed")