I am typing this question in a box that has formatting options above and a little drag down thing on the bottom, that lets me expand the box if my question (or answer!) is long.
However, on some sites like Codegolf, questions can get very lengthy as they have to be specific about things like rules and giving example test cases. I myself have written a Codegolf challenge in the past and I noted that it was really annoying to have to drag the bar down a bunch of times so that I could easily see my whole response without having to scroll.
Can we have a 'fullscreen' button?
If you browse reddit and have RES installed you will see that when typing a comment or a post there will be a button for 'Big editor'; this is exactly what I am talking about. It also has a 'live preview' on the side, while here its below. It would be nice I guess if the preview was on the side.