Looks like this problem has not yet been solved. I found it in several places: Lesson, Book, Label... Martin D. dixit:
The problem with the editor rewriting scripts is an old one for which I don't know the cause or the answer.
This is an excerpt from a 2004 posting... is it still valid? Do we have to wait until we can use another editor?
Cheers,
Pablo
P.S. Joseph Rézeau, thanks again for the workaround you gave me before, it worked like a charm.