Listing lesson: NSE debut shows why mega-IPOs can disappoint despite high demand

New Delhi, Sept. 24 -- The exchange at the heart of India's stock market made a modest debut of its own. The National Stock Exchange (NSE) listed on the BSE at Rs.1,800 a share on Thursday, a 0.84% premium to its Rs.1,785 issue price, and ended the session about 1.8% above the offer price, even as…