How do I delete a comment or reply?

If you just want to delete one of the replies, open the comment box by double-clicking the yellow comment icon. When you hover over one of the replies, you'll see the X button that you can click to delete the reply.

Delete button for comment reply

If you want to delete the whole annotation, single click the comment icon so that you see an orange outline and hit delete on your keyboard (just like you can delete any other element).

Delete entire annotation