Good question!
Only the Super Admin in PowerCMS will see the Developer Notes. However if you were to hand this off to a client, we would recommend that you create a new Administrator account for the client to use.
Any additional accounts have limited functionality to avoid causing problems or frustrations for the client. If you log in as one of these additional admins, you will see that Developer Notes do not display on content (as this assumes the Developer Notes were already handled by the Developer), but for template pages, a Create Link option is available instead.
This way, your client will be able to create pages based on templates, and should be able to find the link to that new "page" without too much trouble or being overwhelmed by the Developer Notes code.
Another thing to note...
The Help page in PowerCMS contains various tips on how to do things in PowerCMS. This help is mostly targeted towards the end-user or client that will use PowerCMS using a non-Super Admin account. However if you are logged in as a Super Admin, you will see a few additional tips at the top of the Help page that are labeled "SuperAdmin Only".
