Accepting an empty pin

Playing with the Web UI, I found out today:  When you click on a document to put a pin somewhere, the Chat pain gives you Add, Add Defect - and our green arrow.  So you can technically 'accept' a pin with no text at all.

Does anyone use this?   Maybe on a drawing or something to show that "I saw this and am happy with it".   

I'm just not quite sure how it would be used - but I assume someone uses it, as the check box isn't greyed out in this instance...

Anyone?