[Markus Ernst]

Thank you both for your valuable info. I encountered that Word does
actually take over the show/hide gridlines settings at the next startup;
I assume I was not aware of this because I changed settings when more
than one document was open, so the changes did not affect all open
instances of Word.

So, though Jay's trick of applying white borders works well, I don't
change them and leave the choice of the preferred view to the user.