This episode was interesting. It did a lot with Houtarou's character and also had some good stuff from Chitanda, plus some more info about Houtarou's sister who is the best puppet master of them all. I liked Chitanda better after this ep. She wasn't so over the top in the "I'm curious!" department, and she seemed to gain more depth. Anyway, in the end, this story arc was about building Houtarou up and knocking him down. The way he was left alone without the others to formulate the flawed theory is proof of that, because if any of them had been there, they would clearly have corrected that solution.
I found it odd the way that all of the characters were so serious about the mystery. Well, maybe not so much Mayaka, but Satoshi, Chitanda to a degree, and especially Houtarou were just silly over it. Even though to Houtarou there was a lot riding on it (with him having believed Irisu when she said he was special and all and then being crushed by his mistakes and all the others rubbing it in) it just didn't seem quite right. He ought to have been aware that Irisu was only looking for an ending she could present as a result. There was never any indication that she cared about solving the true mystery. Heck, if I remember right, Houtarou already declined to write an ending for them, so he knew it was a possibility.
Still, that manipulation of him was harsh. All that fuss just to get a script ending. Calling them in, then puffing up Houtarou's ego to get him to deliver a solution. It seems ridiculous that she couldn't think up an acceptable script solution off her own bat.
I like the theories people came up with here better than the true one.
