How to edit or delete comments in drafts?

Open the draft to which the comment you want to change is added and click on the Comments icon on the right-hand sidebar. A list with all active comments will be displayed. Use the filter in the top right-hand corner to switch the view to only resolved comments: 

How to make changes to active comments?

Simply find the comment you want to amend in the list and click on it. This will open a dialog box in which you can Resolve the comment from the blue label in the top right-hand corner.
If you click on the three small grey dots to the right of the comment, you will be able to edit or delete it.

Note: You can only edit or delete a comment if you have created it.

How to make changes to resolved comments?

If you filter the Comments view to resolved comments, they will be displayed in the right-hand sidebar instead. This allows you to Reopen a comment which will automatically make it active again. 

From the dialog box associated with it, you can now make the same changes described in the previous step.