I've just come across a feature in Excel which I've never seen before. When I click on a cell it displays as a pop-up box with comment-friendly text inside. The pop-up can be dragged around the sheet but I can't find a way of editing the text or deleting it completely. If I click off the box, it hides.
It's not a Comment because I can insert and edit one of those in the same cell as the pop-up.
I've attached a PNG of it.