If I rub my finger in the text entry field, the top of the screen changes

If I rub my finger in the empty text entry field (A), the top of the screen(B) changes.

I can get it to change to the topic title I’m replying to, or toggle back to as you see above.

I’m not sure if this is a bug or a feature.

It’s because you are scrolling up and down the topic behind the editor. The header response makes sense but I’m not sure if scrolling inside the text editor = scrolling in the topic is intentional