I'm trying to follow that argument but, I don't think I agree.
Big amounts of the ninjamined stash has been sold in the past to other buyers, yet the encumbrance did not get transferred to those buyers. Why should it be any different when the buyer is Justin? Just because he bought the entirety of the remaining stash?
Since Steemit Inc is a sole proprietorship, let's try to pierce the corporate veil and see how this looks: The ninjamined stash was, effectively, Ned's. He promised the proceeds of any sale would go to Steem's development. Now, Justin came and bought that stash of STEEM (again, as others have before, albeit in smaller quantities), paying good money for it. Ned simply cashes out, grabs the cash and walks away, A.K.A. an "exit scam", which totally violates his past promises.
I do not see how the attached strings would transfer to Justin. He just made a perfectly legal purchase. Ned did not misrepresent the property being sold. Ned is still bound by the promises he made and he must thus dedicate the proceeds of that sale to Steem.
RE: Justin Sun Conversation with Witnesses Is Online. @Ned Sold Out The Community - Failed to Disclose.