Here it is, the column you've all been requesting in your sly, subtle ways for the past few weeks. I can't hold out against that much fervent demand! So mount up and ride along as we trace Supergirl's exciting adventures with Comet, the Super-Horse from CBG #1591 (May 14, 2004): Supergirl’s Super-Horse! Comet the Super-Horse was Kara's best friend in both human and animal form Dear Mr. Silver A…