You seem to argue (by the use of "glibly") that the presence of the transferability clause leaves no other interpretation possible than that that transfer will

You seem to argue (by the use of "glibly") that the presence of the transferability clause leaves no other interpretation possible than that that transfer will be for use of user content by third part in return for payment. However, the clause may also be there to allow use of content on other services owned by Instagram's parent. I was quite explicit that I was giving my read of the intent, not my assessment of what Instagram could legally get away with. The transferability clause does not change my reading of the intent.