The easiest way to remove notes from your feedback is as follows:
Click on 'Reporting' at the top of the page and go to 'Feedback results'.
Go to the feedback item you want to edit and click on it. Note: make sure your date selection and report is correct (just to prevent searching for a specific feedback result in the wrong date selection or report).
When there's already a note added to your feedback item, like in the image below, you will see 3 icons (bell, pencil and trash) right next to your note.
Click on the 'Trash' button and then on 'Delete'.
Now your note is successfully deleted.