"Leslie is having lunch."
Right. Also, some Hungarian emigrants anglicize their names, and László becomes Leslie or Les, (e.g.: Les Murray, Australian-Hungarian TV-presenter. I never realised he was Hungarian with such an Anglo-Saxon name, until he was a guest on a Hungarian special of a World Food show, making lécsó!)
Still, agree: maybe the "English translations" should be accepted, but I would take out all the recommendations to use "John" or "Leslie", or: Zsuzsi as "Susie" (I don't know why, but that last one really creeps me out, completely changes her personality!)
My father's name was László and it was anglicized to Leslie when we moved to Canada. His father was Lajós and HE anglicized it in our photo album as Louis. My name was Zsusanna (Zsuzsi) and I became Susie. My brother was András (Bandi) and he became Andrew (Andy). My mother's name was Klara and the minor modification there was changing the K to C, so Clara.
During waves of immigration to the new world the latest to arrive were the underdogs. Immigrants struggled to assimilate and avoid discrimination. There was always a new group to look down on.
It is only recently that I see people reverting to or keeping their given name, especially in cinema credits and book titles. Hollywood in the 20th century promoted "ethnic cleansing" of people's origins especially if their names were difficult to spell or pronounce in English, or if they were Jewish.
Sometimes. you will be incorrect if you leave off the accent from Péter when you translate to English and other times you are incorrect if you don't keep it on. Sometimes János is just János while other times it becomes Janos without the accent or John. Consistency please!