there is a way to enable it by default, so you just scroll down and start typing.You have to (as best as I can tell) manually click on the pencil icon in the bottom right corner of any of the posts in the thread, which then allows you to use the 'quick reply' window at the bottom of the screen. If you want to quote that post then you click the "quote post in quick reply" box after you enter the reply. You have to do this every time. If there is a better way, I don't know it.