Posting is more than unweighting the saddle, it's also following through. What I suggested for potholes in that "Hoping for potholes" is exaggerated posting. It's a much more appropriate term for fixed gear riding than general cycling. Sheldon is the smart. You can just unweight the saddle coasting but fixed unweighting the saddle is more akin to hurdling than just bumping over something. Just like on horseback if all you did was unweight the saddle in a jump it'd be unpleasant. Exaggerate the motion and it's great for potholes, less energy than a bunny hop and looks way more fluid.