As far as special characters: I had copied some greek symbols from Safari. Now I'm only using those from the iOS Greek keyboard. (I'm using Greek because I'm coding routines from an astrodynamics book that uses lots of math-greek symbols, and the code is easier to check against the math by making it look similar.)
I'm forcing a save after some tedious coding by backing out to the file navigator and into the file again. Much easier that having to re-enter code that was lost to the crash.
Also, I wondered if the crash was happening due to the device being low on memory. So I rebooted, and haven't seen the crash since; though I've also taken the precautions I mentioned before.
It would be helpful if the app showed a 'file changed' mark between auto-saves. As things are, I'm forcing the save so I don't lose my work.
Thanks all for the responses. :-)