Please remove the delete option from the comment box since the user can accidentally delete the comment instead of closing it.
A long press on the icon should open options for deletion of the comment box.
THanks for using Xodo and your feedback! In case you accidentally deleted comment box, you can undo the action as described here: http://feedback.xodo.com/knowledgebase/articles/1071037-undo-redo.
Hope it helps!