Just wanted to thank the OP, Nezix, for starting this thread. I briefly touched upon this question in another thread, and I had vaguely thought of making a thread about this, but I'm still writing my feedback, and thus confined to a quick-comments-only jail (of my own making).
From what I've read here, with arguments for different perspectives (if you don't mind me phrasing it that way ...), I feel confirmed in the idea that the high-ground rule has no real-life/simulationist justification. (Which is different from tactical/gaming justifications.)
Now, the other big question on my mind :
How much of this whole, indiscriminate "high-ground gives superiority" myth start with Revenge Of The Sith ?
I'm still talking about one-on-one ranged combat (I understand the advantages for a medieval or early-modern army).
Any pop culture historian around here ?