added note about not all tasks being 'delegatable'

docs/docsite/rst/playbooks_delegation.rst

@@ -11,10 +11,11 @@ Additional features allow for tuning the orders in which things complete, and as
 
 This section covers all of these features.  For examples of these items in use, `please see the ansible-examples repository <https://github.com/ansible/ansible-examples/>`_. There are quite a few examples of zero-downtime update procedures for different kinds of applications.
 
-You should also consult the :doc:`modules` section, various modules like 'ec2_elb', 'nagios', and 'bigip_pool', and 'netscaler' dovetail neatly with the concepts mentioned here.  
+You should also consult the :doc:`modules` section, various modules like 'ec2_elb', 'nagios', and 'bigip_pool', and 'netscaler' dovetail neatly with the concepts mentioned here.
 
-You'll also want to read up on :doc:`playbooks_reuse_roles`, as the 'pre_task' and 'post_task' concepts are the places where you would typically call these modules. 
+You'll also want to read up on :doc:`playbooks_reuse_roles`, as the 'pre_task' and 'post_task' concepts are the places where you would typically call these modules.
 
+Be aware that certain tasks are impossible to delegate, i.e. `include`, `add_host`, `debug`, etc as they always execute on the controller.
 .. _rolling_update_batch_size:
 
 Rolling Update Batch Size