Rules?

I am starting to think that there are no strict rules for sight-reading.
I have been trying to play and teach my students to read chords down/up all my life and here I am now, experiencing a lot of improvement with my new way of reading chords. However, even my new way should not be set as a rule. The truth is, we should be making quick decisions as we read. I hope with practice I can get better at it.
The same thing applies to the fingering. There are several ways of doing them. A quick decision also has to be made.
Today, as I sight-reading a few Scarlatti Sonatas, I found it impossible to keep my eyes always on the score. There are several jumps that I could never have played without looking at the keys. I did not have any problems going back to the score. There is plenty of time to do it. Maybe this "rule" about never looking at the keyboard should be enforced only with beginners.
What do you think?