alt Hacker NewsThe author didn't say it was not English.
The author wrote: "I can't use "else" as a conjunction in normal speech, only in computer programs."
No doubt people use 'else' as a conjunction now, due to the influence of programming.
To show the author is completely wrong requires finding pre-1959 uses of 'else' in a conjunction.
https://books.google.com/ngrams/graph?content=else&year_star...
Google ngrams shows 'else' being used fairly consistently up until about 1880 after which it gradually declines. In the 2000s it rapidly picks up, probably because of the programming influence.
Looking at the actual texts, there are a few German ones listed. Plenty with "someone else", "nothing else". Quite a lot with "or else", for example: "Yea , but what am I ? a scholar, or a schoolmaster, or else some youth".