Really liked this chapter and hoping for an update on Chapter 4 soon. The only part that confused me a bit was the communication mirrors. Up until then, every rule and trick of the mirror world made sense. However, the game did not really explain how two mirrors could be connected to two peoples' unique locations as opposed to a reflection of the room. On my second playthrough, it occurred to me that the mirrors could be each other's twin, which could explain the phenonium.
Edit: Wow! Did not expect you to be checking comments. Thanks for letting me know Chapter 4 is on its way. "The Splitting" is definitely one of my favorite web series. Good luck on development :)