Trying to follow http://twocentstudios.com/blog/2012/11/15/simple-ajax-comments-with-rails/

_comment.html.erb

  <div class="comment" id=<%=comment.id %>>
      <div class="well"><%= comment.body %><br>
        <%= comment.user.username %>
      	<small><%= comment.updated_at.strftime('%b %d, %Y at %I:%M %p') %></small>
      	<%= link_to "×", comment_path(comment), :method => :delete, :remote => true, :confirm => "Are you sure you want to remove this comment?", :disable_with => "×", :class => 'close' %></div>
  </div>

_form.html.erb

<h3>Add Comment</h3>

<div class="comment-form">
<%= simple_form_for @new_comment, :remote => true do |f| %>
  <%= f.error_notification %>

<%= f.input :body, :input_html => {:rows =>"4"}, :label => false %>
<%= f.hidden_field :commentable_id, :value => @new_comment.commentable_id %>
<%= f.hidden_field :commentable_type, :value => @new_comment.commentable_type %>
<%= f.submit "Submit", class: "btn btn-primary", :disable_with => "Submitting..." %>
<% end %>
</div>
<br clear="both">

comments.js

(function() {
  jQuery(function() {
    $(".comment-form").on("ajax:beforeSend", function(evt, xhr, settings) {
      return $(this).find('textarea').addClass('uneditable-input').attr('disabled', 'disabled');
    }).on("ajax:success", function(evt, data, status, xhr) {
      $(this).find('textarea').removeClass('uneditable-input').removeAttr('disabled', 'disabled').val('');
      return $(xhr.responseText).hide().insertAfter($(this)).show('slow');
    });
    return $(document).on("ajax:beforeSend", ".comment", function() {
      return $(this).fadeTo('fast', 0.5);
    }).on("ajax:success", ".comment", function() {
      return $(this).hide('fast');
    }).on("ajax:error", ".comment", function() {
      return $(this).fadeTo('fast', 1);
    });
  });

}).call(this);

comments.js.coffee

# comments.js.coffee
    jQuery ->
      # Create a comment
      $(".comment-form")
        .on "ajax:beforeSend", (evt, xhr, settings) ->
          $(this).find('textarea')
            .addClass('uneditable-input')
            .attr('disabled', 'disabled');
        .on "ajax:success", (evt, data, status, xhr) ->
          $(this).find('textarea')
            .removeClass('uneditable-input')
            .removeAttr('disabled', 'disabled')
            .val('');
          $(xhr.responseText).hide().insertAfter($(this)).show('slow')

      # Delete a comment
      $(document)
        .on "ajax:beforeSend", ".comment", ->
          $(this).fadeTo('fast', 0.5)
        .on "ajax:success", ".comment", ->
          $(this).hide('fast')
        .on "ajax:error", ".comment", ->
          $(this).fadeTo('fast', 1)

comments_controller.rb

# comments_controller.rb
    class CommentsController < ApplicationController
def create
        @comment_hash = params[:comment]
        @obj = @comment_hash[:commentable_type].constantize.find(@comment_hash[:commentable_id])
        # Not implemented: check to see whether the user has permission to create a comment on this object
        @comment = Comment.build_from(@obj, current_user, @comment_hash[:body])
        if @comment.save
          render :partial => "comments/comment", :locals => { :comment => @comment }, :layout => false, :status => :created
        else
          render :js => "alert('error saving comment');"
        end
      end
      def destroy
      @comment = Comment.find(params[:id])
      if @comment.destroy
        render :json => @comment, :status => :ok
      else
        render :js => "alert('error deleting comment');"
      end
    end
    end

show.html.erb

<div class="row-fluid">
  <div class="span8">
		<div class="well">
			<% for pinimage in @pin.pin_images do %>
			<%= image_tag pinimage.photo unless pinimage.photo_file_size.nil? %>
			<%= pinimage.caption.to_s %>
			<% end %>
			<br><% if current_user == @pin.user || current_user.admin == true %> <%= link_to 'Edit', edit_pin_path(@pin) %> | <% end %> 
<%= link_to 'Back', pins_path %>
		</div>
</div>
<div class="span3">
	<ul class="unstyled">
  <li><b>Surgeon:</b>
  Dr. <%= @pin.surgeon %></li>
  <li><b>Procedure:</b>
  <%= @pin.procedure %></li>
  <li><b>Cost:</b>
  <%= @pin.cost %></li>
  <li><b>Want revision?:</b>
 <li><%= @pin.revision %></li>
 <li><b>Description:</b>
  <%= @pin.details %></li>
</ul>
<small><b>Submitter:</b> <%= @pin.username %></small>
</div>
<br clear="both" />

<%= render :partial => 'comments/form', :locals => { :comment => @new_comment } %>
<%= render :partial => 'comments/comment', :collection => @comments, :as => :comment %>