Notes for Managed Forms
If you drag and drop a Notes control onto a CRM form that you will be rendering with a managed form, that notes control will appear on the portal. No notes will appear, however, unless Entity Permissions have been explicitly granted, either on a global or entity-specific level, for the Notes (annotation) entity. This is true whether you have enabled permissions on the Entity Form or Web Form that is rendering the Notes control or not. It's wise to use Parental Permissions to enable access to notes rather than enabling access globally, because doing otherwise will open up all note attachments to direct access by users regardless of their role, due to the fact that they can access annotation URLs by GUID.
When notes are created on the portal (such as when you've configured the Notes control for editing using metadata), they will have this prefix automatically.