I like to think of HN conversations as taking place in a third or fourth year university elective course. You are here because you want to learn something. Hence, all comments should be substantive and contribute to the learning of the class. In this scenario, jokes should be occasional, and should be embedded in a larger constructive comment, much as they would be in actual university class.
I was about to say something nearly identical to this, but couldn't have put it better than you did! In this specific scenario, I think the joke was in good taste and might even spawn some serious discussion and questioning (as seems to be the case already).
In fact, I came to this thread wondering if such a comment (about Erlang) would be made, and I was not disappointed. I am an Elixir (/Erlang/Gleam/BEAM/OTP) fanboy and WhatsApp is basically the canonical example of OTP's strengths, so perhaps I should be outraged! But I am not, and that says a lot about the quality of the joke (it's not a "Reddit-style" joke - it actually makes one think). It's fun and enlightening to consider the ways in which Erlang's reliability guarantees can be hamstrung by (presumably) external factors such as DNS/hardware/BGP, and a good reminder that things are messier than just which language or platform one chooses.
Anyway, yes. I would distinguish between enlightening jokes that arouse curiosity, and Reddit-style low-quality "humor" and trolling.