There seems to be plans in place to open the bitcoin-central again soon having that set of customers suffer no losses I am wondering whether it is legal to favour bitcoin-central customers over Instawallet customers in this situation if there are same companies involved and if they are insolvent?
There is a significant difference in the relationship between Bitcoin Central and its costumers as opposed to Instawallet and its costumers. Bitcoin Central did have an authentication system, which did provide their costumers with more protection. In the end Instawallet users lost their bitcoin to a database hack, BTCentral was just running on the same servers. Many users made a well-reasoned decision to stay away from Instawallet and still used BTCentral.