We devote this commentary each week to assessing the many reasons markets may rise or fall. But at the heart of it, all markets come down to just one thing: buyers and sellers. Taking a look at who is buying andwho is selling can tell us something about the durability of the market’s performance and what may lie ahead. Currently, there are six notable trends in buying and selling in the stock market. U.S. stocks are being purchased by corporations and individuals; however, foreigners, hedge funds, institutions, and insiders are net sellers. Companies themselves have been the biggest buyers of stocks. After reducing purchases during the financial crisis in 2008 and 2009 as companies focused on hoarding their capital, corporations have returned to record levels of net share repurchases….