In careers, when you click inside a text input box, you will often see a popup appear to the right. It'll give you some tips as to what to do, what to say, etc etc.
As I pondered a personal statement earlier, I moused over the popup. My cursor changed to signify that I was hovering over text that I could interact with. However, when I attempted to highlight some text (for no particular reason), the popup disappeared.
While yes, it's not incredibly important, it appears that you can interact with the element, and then it disappears when you try. I would say the box should not disappear when clicked on, but should provide a small x in the corner to close it.