finally got it to work! (I hope…)

client/helpers/router.js

@@ -255,14 +255,14 @@ PostsListController = RouteController.extend({
     Session.set('postsLimit', limit);
 
     // get posts and decorate them with rank property
-    // note: not actually used; find better way
+    // note: not actually used; 
     // posts = posts.map(function (post, index) {
     //   post.rank = index;
     //   return post;
     // });
 
     return {
-      posts: posts
+      postsList: posts
     }
   },
   after: function() {

client/views/posts/post_item.js

@@ -77,54 +77,38 @@ Template.post_item.helpers({
   }
 });
 
-// var recalculatePosition = function ($object) {
-//   var pArray = $object.data('positionsArray'),
-//       top = $object.position().top;
-      
-//   if(typeof pArray !== 'undefined'){ 
+var recalculatePosition = function ($object, pArray) {
+  // delta is the difference between the last two positions in the array
+  var delta = pArray[pArray.length-2] - pArray[pArray.length-1];
 
-//     // if current position is different from the last position in the array, add current position
-//     if(top != pArray[pArray.length-1]){
-//       pArray.push(top);
-//       $object.data('positionsArray', pArray);
-//     }
+  // if new position is different from previous position
+  if(delta != 0){
+    // send object back to previous position
+    $object.removeClass('animate').css("top", delta + "px");
+    // then wait a little and animate it to new one
+    setTimeout(function() { 
+      $object.addClass('animate').css("top", "0px")
+    }, 1);  
+  }
+}
 
-//     // delta is the difference between the last two positions in the array
-//     var delta = pArray[pArray.length-2] - pArray[pArray.length-1];
+Template.post_item.rendered = function(){
+  var instance = this,
+      $instance = $(instance.firstNode.nextSibling),
+      top = $instance.position().top;
 
-//     // if new position is different from previous position
-//     if(delta != 0){
+  // if this is the first render, initialize array, else push current position
+  if(typeof instance.pArray === 'undefined'){
+    instance.pArray = [top]
+  }else{
+    instance.pArray.push(top);
+  }
 
-//       // send object back to previous position
-//       $object.removeClass('animate').css("top", delta + "px").addClass('animate');
+  // if this is *not* the first render, recalculate positions
+  if(instance.pArray.length>1)
+    recalculatePosition($instance, instance.pArray);
 
-//       // then wait a little and animate it to new one
-//       setTimeout(function() { 
-//         $object.css("top", "0px")
-//       }, 1500);
-    
-//     }
-//   }
-// }
-
-// Template.post_item.rendered = function(){
-
-//   var instance = this,
-//       $instance = $(instance.firstNode.nextSibling),
-//       top = $instance.position().top;
-
-//   instance.renderCount = (typeof instance.renderCount === 'undefined') ? 1 : instance.renderCount+1;
-
-//   if(instance.renderCount>1){
-//     // when one post re-renders, force all of them to recalculate their position
-//     $('.post').each(function(index, item){
-//       recalculatePosition($(item));
-//     });
-//   }else{
-//     $instance.data('positionsArray', [top]);
-//   }
-
-// };
+};
 
 Template.post_item.events = {
   'click .upvote-link': function(e, instance){

client/views/posts/posts_list.js

@@ -1,13 +1,12 @@
 Template.posts_list.helpers({
-  // posts : function () {
-    // not used, forces multiple re-renders
-    // this.postsList.rewind();    
-    // var posts = this.postsList.map(function (post, index, cursor) {
-    //   post.rank = index;
-    //   return post;
-    // });
-    // return posts;
-  // },
+  posts : function () {
+    this.postsList.rewind();    
+    var posts = this.postsList.map(function (post, index, cursor) {
+      post.rank = index;
+      return post;
+    });
+    return posts;
+  },
   allPostsLoaded: function(){
     return false;
     // TODO: find out when all posts have been loaded