In the pages test instance, if you add a comment to a test step there is no cancel button

If you press on the add comment button in the test instance and this is not what you want to do, there is not "cancel" button. Thus is this is not what you want to do, you need to reload the page before you do any other action, otherwize you get a form validation error saying that the "comment is empty"

Note that I have found out that if you click again on the "green plus sign", this is like doing a "cancel"