Vulcan/client/views/comments/comment_list.js

Template.comment_list.created = function(){
  postObject = this.data.post;
  rootComments = Comments.find({post: postObject._id, parent: null}, {sort: {score: -1, submitted: -1}});
}

Template.comment_list.helpers({
  has_comments: function(){
    // note: use this.post to access 'post' object in router data context
    if(this.post)
      return rootComments.count() > 0;
  },
  child_comments: function(){
    // return only root comments
    return rootComments;
  }
});