Hmm, that is
a toughy. Yeah, like Marnie says, I try to avoid increasing twice in the same stitch, because it creates a hole.
The only other thing I can think of, is increasing in a stitch you've just decreased, because "what would be the point." But of course, I've seen it done for a neat effect. IMHO, there's really no "nevers" in knitting! There's always those times when you break the "rules," either for effect, or for convenience.
Let us know what the "correct" answer turns out to be! Now you've got us curious!