That makes Fidelity's insider buying and selling activity a potential tell on whether the biggest owner of Green Mountain shares still has conviction in this stock. Recent activity in the Fidelity funds shows that buying and selling "wash" when it comes to Green Mountain. Even though the last full quarter portfolio update from Fidelity is as of June 30, the funds each reported on their own as of the end of the Sept. 30 quarter. Fidelity Mid-Cap, which has the largest holding in Green Mountain, had sold a net 931,000 shares of Green Mountain. Yet Magellan had added more than 2.3 million shares as of Sept. 30. Contrafund had sold 139,000 shares and Fidelity Growth Company had no net position change in Green Mountain. Of course, the Sept. 30 period pre-dates the value investing conference where Einhorn went public with his short in mid-October, so it's Fidelity's action from here on out that investors should watch for any "tell" from the fund giant that its managers aren't buying and selling individually, but making a conviction call -- either dump or buy on the dip -- in Green Mountain shares. What's more, Morningstar's Kinnnel said that with a stock like Green Mountain -- not a blue chip large-cap -- it is likely that Fidelity has one analyst who is the "conviction" decision-maker across all of its funds, even if the funds diverge on quarter to quarter buying and selling, and given the recent action in Green Mountain shares, this might be a time when the fund giant's portfolios all move in the same direction. If Fidelity has upped its ante in Green Mountain during the third quarter -- which we won't know for a while yet -- it would suggest there is at least one big shareholder, the biggest in Green Mountain, who isn't running scared of Einhorn or one bad quarter, or the big inventory build at Green Mountain, and its massive spending plan increase. If, on the other hand, Fidelity starts dumping Green Mountain shares en masse -- or already has -- buying on the dip would put the average investor at odds with the one of the biggest fund companies out there. "With 10% to 12% ownership in this stock it does mean that they Fidelity have some impact, if they all want to sell or all bought at the same time, and especially if the latest news has a bunch of their managers queuing up to sell," Morningstar's Kinnel noted. -- Written by Eric Rosenbaum from New York.