I’m a big fan of this one! I know there are popular (VERY
popular) writers who shift POV within scenes, within paragraph, sometimes
within sentences. For the life of me, though, I can’t figure out how to read
those writers.
I have to use clean POV for my own sanity. If I’m in Mary’s
head, there has to be a break before I hop over to Jane’s head. It can be a new
scene. Or it can be the same scene repeated from an alternate POV. I kind of
like to do those when I can manage them.