PERF: Do far fewer checks and use a lot less memory when loading more

app/assets/javascripts/discourse/mixins/load_more.js

@@ -15,9 +15,8 @@ Discourse.LoadMore = Em.Mixin.create(Ember.ViewTargetActionSupport, Discourse.Sc
     if (eyeline) { eyeline.update(); }
   },
 
-  didInsertElement: function() {
-    this._super();
-    var eyeline = new Discourse.Eyeline(this.get('eyelineSelector'));
+  _bindEyeline: function() {
+    var eyeline = new Discourse.Eyeline(this.get('eyelineSelector') + ":last");
     this.set('eyeline', eyeline);
 
     var self = this;
@@ -25,11 +24,10 @@ Discourse.LoadMore = Em.Mixin.create(Ember.ViewTargetActionSupport, Discourse.Sc
       self.send('loadMore');
     });
     this.bindScrolling();
-  },
+  }.on('didInsertElement'),
 
-  willDestroyElement: function() {
-    this._super();
+  _removeEyeline: function() {
     this.unbindScrolling();
-  }
+  }.on('willDestroyElement')
 
 });

app/assets/javascripts/discourse/models/user_action.js

@@ -193,7 +193,7 @@ Discourse.UserAction = Discourse.Model.extend({
 Discourse.UserAction.reopenClass({
   collapseStream: function(stream) {
     var uniq = {},
-        collapsed = Em.A(),
+        collapsed = [],
         pos = 0;
 
     stream.forEach(function(item) {

app/assets/javascripts/discourse/views/user-stream.js.es6

@@ -14,6 +14,7 @@ export default Ember.View.extend(Discourse.LoadMore, {
       var self = this;
       if (this.get('loading')) { return; }
 
+      this.set('loading', true);
       var stream = this.get('controller.model');
       stream.findItems().then(function() {
         self.set('loading', false);