Some fixing up on the Russian romanization.
KH is accepted for Х (Kha/Ha). Why not also H & X. There would never be an ambiguity. For example: Ya khochu pit. Ya hochu pit. Ya xochu pit.
The purpose of "kh" is to show that it's a different sound from both "k" and "h", and it's definitely different from "x", which sounds as "ks". So "kh" was chosen (similar to the German sound "ch").
Separate conventions utilize all 3: Kh, X, H. Latin X, if also used to represent sound of Kha from Russian would not cause a confusion betweem "h" sound and "-cks" sound. Ya Hochu pit versus Ya Ksochu pit. It would not happen.
I did not know that, very interesting! Still, I would find "x" and "h" a bit confusing, I don't think they do a good job of representing the sound (especially if read by non-learners of Russian). But then again, I only read Russian written in the Cyrillic alphabet, which takes care of the problem.
I would find "x" and "h" a bit confusing .. how so? I am curious. When I text my Russian speaking friends I usually transliterate. Now bear in mind these are Russians who have some command of English. If i put Horosho or Xorosho they don't appear confused.
I find Xorosho moe natural than Khorosho. But that is my own slant. Maybe different for someone else.
As I said I only ever use the Cyrillic alphabet, that's probably why those transliterations look weird to me, I think I'm just not used to them. But I certainly prefer "x" over "h", since many beginners pronounce Х as "h", and that transliteration might somehow reinforce that (or maybe not?).