Everything you have done is correct, except for view definition

Place the oe_chatter div inside form, but after the sheet, hence your code should like this

    </sheet>
    <div class="oe_chatter">  
        <field name="message_follower_ids" widget="mail_followers" groups="base.group_user"/>  
        <field name="message_ids" widget="mail_thread">
    </div>
</form>

Further if you just need the Chatter box, then ''mail.thread' alone is enough, 

However if you need notification on unread messages on the List/Tree view then use ''ir.needaction_mixin', along with the associated field 'message_unread' in the Tree View, something like below

<tree fonts="bold:message_unread==True" string="TREE VIEW">                    
    <field name="message_unread" invisible="1"/>

Hope this helps you.

I found a solution, but it's incredibly ungraceful and may impact more than just this module.

Inside your view (or if you are already loading CSS files), do something similar to below

<form string="Test">
  <style>
    .openerp .o_form_invisible { display: block !important; }
  </style>
// The rest of your form
  <div class="oe_chatter">            
    <field name="message_follower_ids" widget="mail_followers" groups="base.group_user"/>            
    <field name="message_ids" widget="mail_thread"/>          
  </div>
</form>

This is not optimal because it may override other things that should be marked invisible and it forces use of !important for every future override that needs to be done with this class.

Manually adding a different class to show the element will not work as CSS rules are evaluated on a "What was added last" basis, and o_form_invisible gets added after any manually added classes.

Hi, try to put it after the sheet closing and before the form closing :

                    </sheet> 
                      <div class="oe_chatter"> 
                               <field name="message_follower_ids" widget="mail_followers"/> 
                               <field name="message_ids" widget="mail_thread"/> 
                      </div> 
               </form>