From Adobe's help in Enable and disable Design Notes for a site :
- Select Site > Manage Sites.
- In the Manage Sites dialog box, select a site, then click Edit.
- In the Site Setup dialog box, expand Advanced Settings and select the Design Notes category.
- Deselect Maintain Design Notes to disable Design Notes
- If you want to delete all local Design Notes files for your site, click Clean Up, and then click Yes. (If you want to delete remote
Design Notes files, you’ll need to delete them manually).
Note: The Clean Up Design Notes command only deletes MNO (Design
Notes) files. It does not delete the _notes folder or the dwsync.xml
file inside the _notes folder. Dreamweaver uses the dwsync.xml file to
maintain information about site synchronization.
So although Notes can be disabled, it seems rather a bad idea to delete the _notes folder if you intend doing site synchronization.
You could also try and disable site synchronization
in the Remote Info category of the site definition dialog box.
For more detail see Maintain Synchronization Information site definition preference.
With both settings disabled, Dreamweaver might give up on the _notes folder.