It could be that the effect of insider buying has been muted by the fact that though Kovner's purchases have been enormous, he is so wealthy that he'd suffer no real personal pain if SNTA went to ZERO. In other words, the market may feel the buying doesn't really reflect a hard headed ECONOMIC decision. I don't see a "red flag" in the price action, just the sense that these transactions, rightly or wrongly, aren't conveying the same nature of insider confidence that insider buying normally conveys.
I believe your points are valid but in my opinion what the market is missing is the fact that money is money. It's just that with Kovner it's not as big of an object. He makes a huge gain on a stock and makes 81% if he holds it for a year before he sells. He takes a big loss and all he can write off is the amount of his bracket (which is probably around 33% or so). My point is that he is in for profit, not a write off.