To my mind, this is similar to saying "look but don't touch" about a door handle, an elevator, or a platter of hors d'oeuvres in a crowded party. Of course people are bound to be confused; that's not the way to go about bragging to people about your fragile antique doorknob, guerilla marketing for the Otis elevator corporation or demonstrating what a really well made (prototype) bruschetta looks like.
This isn't merely a cultural issue, where we're used to the availability of code being a signal that it's open source. It's a deeper issue of social cognition than that. Other people are seeing the hatetris post, and making the perfectly normal inferences that humans as sophisticated social creatures are bound to do -- namely that if he's putting stuff up publicly and even points to it enthusiastically, and that stuff offers natural interactions to the reader, then it must be because he intends his readers to partake of those natural interactions with that publicly available stuff. Here the stuff is code and the affordances are reading, copying and changing, but I they needn't be for this error to occur. The OP's just failed to consider that his readership might mistake his exhibiting of untouchable code as an invitation to interact with it.
This is just culture clash. You're coming from a writer background and publishing things for people coming from a hacker background. If you explicitly state "this is not free software: look but don't touch", people will at least understand what your expectations are. Not everyone will understand or agree with you, but most will respect your wishes.
Similarly, I suspect a hacker-turned-writer would be likely to have a similar attitude to his fiction as to his code, and use a CC license. Or artists in general, actually: two examples I can think of are Randall Munroe and Jonathan Coulton.