Sun-Times sports columnist Greg Couch likes to try to outschoolmarm his colleague Jay Mariotti from time to time, wagging his finger and tsking about the venality of sports figures. But this reflex really got out of hand Friday, when he phoned in a column insinuating that Jim Thome, of all people, may have taken steroids. The Pride of Peoria may look like Mr. Incredible, but as Couch should well know, he always has. We’re not talking Pudge Rodriguez, the last couple of seasons looking as mysteriously slim as a gymnast. We’re not talking Jason Giambi, Troy Glaus, Rick Ankiel, or Barry “My Head Has Increased by Two Hat Sizes ” Bonds. What was Couch thinking, pouring poison into the ear about one of baseball’s undeniable good guys, who hit his 500th home run yesterday with a walk-off game winner?