I would like to respond to your question about why we "can't read" in dreams. You apparently are intellectualizing the probability based on cognitive complexity. I disagree with this because your premise is incorrect, so the arguments are arbitrary. I have experienced reading in dreams personally, not only in English but in Archaic (or dead languages). Was I actually reading in my dream or was I just interpreting the act of reading? It is almost moot because the information I gained from the act of reading was retained, in part, upon awakening and I made notes in a Dream Journal as one of my psychology classes (The Psychology of Higher Mental Processes, Wayne State, mixed level grad/undergrad). It was interpreted by my mind in a way that made sense to me. It was a convenient way to explain whatever else was going on in the dream and how the acquisition of information was possible to resolve obstacles.
I propose that we are limited only by our imaginations, our knowledge, and our questions. We synthesize information that we assimilate during our waking hours and process it into our collective cognition, which is evolving, devolving, or stagnant. In your dream, it is not only possible to read, with or without seeing text, whether or not the language is contrived by your imagination or one used in objective reality. In fact, you could imagine becoming the ink on the page and writing the story from beginning to end with yourself. Do you see my point? When it comes to dreams, you have to keep an open mind. Symbolism is a very interesting aspect of dream interpretation. I suggest you read Carl Jung on dream interpretation. You will learn more about your dreams than you ever thought was possible. Remember, elevate your questions and you will receive elevated answers. All you need is the Will to receive them, even through your dreams.