Not sure if this qualifies as a bug or a feature request. That would depend on your design intentions; however, I have noticed that when working in the Standard editor, once you reach the bottom edge of your screen, new text will simply appear below the viewable area. This forces the user to stop typing in order to scroll the page manually. For an application that is otherwise so well thought out, I would assume that is a bug rather than a missing feature.
Is the Scrivener window perhaps too tall, and partially obscured by your Taskbar? To verify, try clicking the Maximise button and see if a row of buttons along the bottom suddenly pops into view. If it is too tall, that would explain why text is scrolling out of view as you type—it would be under the Taskbar.
To further add to this, there is a little issue at the moment where new projects will open too large so that the bottom is under the taskbar–unless you fix this by dragging to resize the window or by clicking the “maximize” button as Ioa said, your project editor will have a portion out of visible space. This is on Lee’s list to fix, so it shouldn’t be such a problem in the future, but at present it can definitely cause some confusion and might be the matter here.