By MP Mueller November 11, 2010 11:48 am November 11, 2010 11:48 am A few months ago, a Groupon coupon arrived in my in-box from Jeffrey’s Restaurant and Bar, a long-standing premier dining destination in Austin. My immediate reaction — after savoring the vision of bellying up to a half-priced plate of crispy oysters on yucca chips with habanero-honey aïoli — was, “Wow, will discounting be good fo