In answer to your question, Incitatus, the Government couldn't simply persist in saying "no comment" because they would have immediately been accused of a cover-up, especially by the Foreign Affairs Select Committee which was currently investigating Gilligan's report. Just because the Press feel they have to protect their sources, doesn't mean that everyone else has to - after all, if you were an employer and knew that one of your employees had spoken out of turn to a journalist leading to you being accused of deception, would you feel that you had to protect his identity? Personally, I feel that the best course, when Kelly came forward, would have been for the MoD to persuade him to let his name be divulged straightaway, rather than go through a charade, knowing that his name was bound to come out very soon.