That's the whole point. I wasn't explicit about it, but that's what's done by default for other "weird" characters" in the ASCII set. Try ASCII-6 (ACK) for instance. It would be nice if I could extend the same mechanism to include NUL.
thor
Feel the white light, the light within
Be your own disciple, fan the sparks of will
For all of us waiting, your kingdom will come
Comment on Re^4: Displaying NUL in a TK::Text widget