I was thinking that too Andy but everyone is different. Can a person not just delete what they wrote and not send anything or is more of a ( i was going to say something but letting you know i chose not to) sort of thing
Once you delete/edit a comment - it still requires (x) amount of character's to save it. So you have to put something, I usually just put a few xxx's so its not taken the wrong way.
That said , by NO MEANS am I the expert on deleted comments,