part of a prompt is deleted, then the entire prompt must be deleted
and that all prompts must stay at the beginning of a line. If this is
not the case, then `comint-kill-region' behaves just like
-`kill-region' if read-only are involved: it copies the text to the
-kill-ring, but does not delete it.
+`kill-region' if read-only properties are involved: it copies the text
+to the kill-ring, but does not delete it.
+++
*** The new command `comint-insert-previous-argument' in comint-derived