Well, my theory is just pointing out that placing the wall originally at 280 (where it was destabilizing the market), then moving to 320 (where it was getting action), then to 300 isn't rational *unless* you're trying to set up some OTC trade in the other direction and need a "stable" multi-hour average on Bitstamp as a pricing reference for the OTC trade. So to fit that with your theory, you could still argue that it was Pantera executing the final load-up via such an OTC trade, and the 30k wall was theirs and simply necessary for the price-fix. Still fits with your point asking who would trust an unregulated Slovenian exchange with 30kBTC...
Anyway, I honestly don't know what to think. I don't really understand moving the wall from $320 to $300 outside of the price-fix OTC-buy theory which seems a little complicated for my usual liking. But, as I repeatedly say, I'm not a trader, so I have little instinct for how much shenanigans like that actually happen. Maybe it's more common than I think.
6 hours on a Sunday is not enough time, nor even a possible time, to set up an OTC trade of that magnitude.
those things take days, if not weeks to negotiate and setup for that amount.
if you look at the address and read Dan Moorehead's tweets, the 30K BTC were transferred to Bitstamp just before the wall went up on Sunday and the coins originating from that address were accumulated from April 2013.