New Mountain Finance Corp. (NYSE:NMFC) has registered an unusual volume of insider buying this week, as six different insiders bought shares on Monday through Thursday. Nonetheless, we will reveal the most noteworthy insider buys only. To start with, Chairman Steven B. Klinsky purchased 222,313 shares this week at a weighted average price of $13.03, boosting his holding to nearly 3.84 million shares. Director David R. Malpass snapped up a block of 30,000 shares at prices that ranged from $12.17 to $12.93 and currently holds 161,411 shares. Last but not least, President and Chief Executive Officer Robert A. Hamwee bought 25,000 shares on the same day at a weighted average price of $12.35, lifting his stake to 212,459 shares. The business development company mainly invests in debt securities at all levels of the capital structure, which include first and second lien debt, notes, bonds and mezzanine securities. Shares of New Mountain Finance Corp. (NYSE:NMFC) plummeted in early-December, presumably because of the sharp sell-off in junk bonds. First and second lien debt is mainly rated below investment grade, and these debt investments are widely-known as junk debt investments...