I just found a new small bug in A/UX. This bug appears when using TextEditor with an extended keyboard. If you hit the HELP key, an alert appears on the screen. In this alert you can read:
Unable to open the help file "MPW.Help".
#OS error -43 (Error message file not available)
The behavior you describe has been verified. It is a TextEditor bug on both A/UX 2.0 and 3.0.