That chapter gave us a good deal of new information.
Also, note the shadow responded to the call sign. Differentiating real from shadow is going to be a pain. Also, there is an entity controlling the shadows and outside that control they behave very much like the original (it seems).
One potential question is whose thing are we seeing in the reaction and thought bubble text? Is it Shadow Shinpei's? If so is the shadow indeed entirely unaware of their status until the controlling entity takes over again? What knowledge/memories do they retain of the time when are are "activated"? How much of the old personality is left when they are "activated"?