Now that just sound like convenient magic to justify it.
I don't think I've ever seen it mentioned straight out anywhere besides here and Sailor Nothing, but clearly this must be the usual case, seeing how magical girls are never recognized despite almost always looking the same as usual, just with different clothes.
^There's no real need for mind reading in texting, though. Them communicating long distance via texting would be no different from any other people, removing not only the significance of the mind reading, but also of the aphasia. I'm also a bit amused by you saying that Mashiro wouldn't have to write everything down if they text, when texting consists of doing exactly that.
^Although it's also clearly said in the main series in episode 10 when Tougou visits Sonoko again. And you could figure it out even earlier if you realize why Tougou had three fairies from the start.