The easiest way to remove notes from your feedback is as follows:
Click on 'Reporting' on the left of the page and go to 'Feedback inbox'.
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 specific feedback results 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 an icon with three dots to the left of your note. Click on this icon and then click on ‘Delete’.
Now your note is successfully deleted.