Presumably this works exactly like Skype. All new messages are scrolled but if you manually scroll up to read old messages you'll get a button for "new message" that you must click on to resume. Which makes sense in that you don't want the screen to automatically advance if you are manually scrolling for old messages.
No, they broke this in one of the more recent updates. It never scrolls to the bottom once you get more than one window full of messages automatically anymore.
