One of the basic principles of communication is that you have a mental model of the person you're communicating with and are phrasing what you want them to understand in terms that you think they'll understand. So whenever you're writing something - anything - you should be writing with a target audience in mind, and stop explaining right around the point where you believe that your target audience doesn't need further explanation.

Of course it's normal for there to be a disconnect between your assumptions about your target audience and reality. In a real conversation this happens all the time and it's no big deal. When something's written and especially when it's printed it can be a bit more of a problem, so maybe better to err on the side of over-explaining. Also a good reason to have editors and proofreaders. But I'm rambling a bit.

In this case, the link was posted to HN by the author, so the author might have had "average HN reader" in mind. Oberon never really achieved success outside of a particular niche in academia, so unless they went to ETH Zurich I personally wouldn't expect someone - even someone in tech - to know about it.