To erase a device note, go to
Ribbon: DM Electrical->Devices-> 
Erase Note
Pulldown Menu: DM Electrical->Modify Devices->Erase Note
You will be prompted to specify the note to be erased.
Select device note to erase:
The note and associated leader will be erased.
Some notes cannot be erased using this command. These notes will need to removed by changing the definition of the device the note is associated with or changing the option that displays the note.