If it wasn't hard, why should you be praised at all?
Whether the task would have required effort by some other hypothetical person isn't really relevant to the point. It would be appropriate to praise me for completing a marathon, but not Haile Gebrselassie.
To start with, that fails to account for things like moral and ethical choices that don't require significant effort, but should still be praised when the correct choice is made.
More seriously, it distorts self-esteem and worldview. Results become unimportant, it is effort alone that matters. A child raised in such an environment will get its ass kicked in the real world where nobody cares about effort, only results.
Effort must be encouraged as a means to an end, not the end itself.
However, it doesn't seem to me that praising someone for not stealing every day is a good idea either. You should not steal because it's wrong, not because you get praised for it.
I don't know how you interpret the Dweck research as implying that results are unimportant. Why would you expend effort trying to accomplish something that is unimportant? Besides, the research shows that results improve when you encourage a growth mindset, regardless of your philosophical feelings about this.
Comment threads frequently run far away from the specifics of the originally linked article. You're imbuing the conversation with a context that isn't entirely there.
Yeah, in my case that was confusing up until it became insulting, probably somewhere around 7 or 8. Into the teens and adulthood, it might end up encouraging someone to reducing their efforts until they just squeak by, depends on the personality. I'd focus more on figuring out what she actually finds hard or easy, boring or interesting.
Positive reinforcement isn't bad, per se, but that particular statement acts like everything should be hard, which can be just as damaging, albeit in different ways, than acting like everything is easy.
(By the way, if you haven't already, read up on Asperger's syndrome now. A lot of gifted kids have it and go undiagnosed into adulthood. Some end up fine, some end up junkies, almost all have a very confused adolescence and even more confused parents. If your daughter shows any signs, now is the time to start paying attention and trying to compensate. Notably, it can totally screw with how reward works. A lot of us place essentially no value on verbal praise, we require tangible rewards.)