|I can see his face but I can't think of his name...|
Chinese characters aren't unambiguously phonetic, so they can be pronounced multiple ways—in different dialects of Chinese and even in different languages. Still, it hadn't occurred to me that even in the 1970s, Koreans might still call Chinese leaders by the Korean readings of the characters in their names—so that Deng Xiaoping, 邓小平, would become "Deung Sopyeong" when pronounced in Korean.
Interestingly, this practice seems to have stopped at some point. Younger Korean people seem to use the Korean phonetic pronunciation of Deng's Mandarin name; the same is also true of Mao Zedong (Ma-o Jjeodung). But older people might still recognize Mao as "Mo Taekdong." Xi Jinping is just pronounced phonetically; apart from the tones, it transfers perfectly into Korean. He never becomes "Seup Geunpyeong."
It reminds me of how, in early modern Europe, it was common to alter your name to suit the local vernacular, so "John" in England might happily refer to himself as "Jean" in French and then "Johann" in German. I'm not sure when this practice stopped, though I do know that at least into Beethoven's early career, he'd sometimes be referred to as "Louis van Beethoven" or "Ludovico van Beethoven" in foreign editions of his music. Does this practice die out as a result of a kind of linguistic nationalism—the idea that names aren't transferrable between tongues, that there are no real equivalents, that to be Yeong-il in Korea isn't the same as being Yongyi in China, or Marie in France not the same as Mary in England and Miriam in Hebrew? I personally find no discomfort in the notion of moving between version of the same name; but since Spencer was historically not a given name, I suppose the issue isn't really one I'd ever face. I suspect most Johns and Marys would feel pretentious calling themselves Jean and Marie in French. But I'm curious about why and when that sense of imposture started.