Translation:Good evening, he is Christian, I am George.
Not true. Plenty of people choose to adapt their names if they locate to a new country, like Petre becoming Peter or Ion becoming John. There's nothing wrong with knowing the equivalent, especially when so many people do adapt their names.
In addition to that, names DO change across languages. Christina/Kristina, Basil/Vasile, etc. Not your own name, but the name in and of itself changes spelling across many languages. In English, Christian is spelled with an H and this is an English translation so there's nothing wrong with either variation being used (especially when, in this example, the name is even pronounced differently between the two languages).
I disagree. While people might choose to adapt their name, the default should not be to localize everyone's name in every situation. If someone introduces themselves to you as Andrew, would you call them Andrei when speaking Romanian? I would not. From what I've seen, names in other courses on Duolingo have not been localized, and I don't think they should be here either.
Sometimes they decide to change their names. For instance Ştefan changes sometimes to Istvan, especially in Transylvania.
Why on earth is "Gheorghe" not accepted as "George," when they still want us to translate "Michael" as "Mihai?"
You're right, the two have the same origin but they evolved as different names in Romanian. Currently, both exist in Romanian and they are considered distinct names the way John and Ian are considered distinct in English despite having the same root. By contrast, Mihai (or Mihail) is a translation of Michael.