I was thinking about this the other day as well, but I agree with Joe that there isn't a pressing need for it, at least not yet. The benefit of a "quote" button on forums is best seen in very large generic threads with many participants. There, for clarity of response, you want to see the quote author's name and have an automated link back to the original post, which could be on an entirely different page of the thread. But most of the posts here are very focused on a single topic, with few overall participants, and this is probably the biggest and most active example of a mojoPortal forum right now.