What purpose do stories like this serve? People consider asking for details to be rude. Other than tabloid style storytelling drama, why else should strangers care? This man died young, but so did the local 19 year old young woman killed just after midnight by a driver just after she rescued an injured dog from the road. You can already see someone saying the cause of death does not matter, but why does this death an…
This young man's death is just as "important" as the young woman you mention...they are both tragedies, they both will leave an indelible wound on many people's lives.
However, this is a social news site for the tech community. The young woman's death is not covered here because it's not relevant to the tech community.
This young man started (with others) a project which is followed, used, and worked on by many in the tech community...it's of interest to them that one of the initiators died just as any other major development would be. It's also safe to say that there are a few people here who either knew him personally or had had some interaction with him, so it's of interest to the community when one of it's own dies.
Any time you load Hacker News there will probably be some stories that don't interest you. However, as long as they follow the community guidelines, are relevant to hackers, etc...it's best to simply skip them.
As for your other point(s), I agree somewhat with what you seem to be saying. I don't think it's rude per se to respectfully ask if anyone happens to know the cause of death. I would find it more rude to speculate. I also agree that a bunch of strangers offering their condolences doesn't accomplish or mean much, but I can also appreciate that people are just trying to be nice to anyone who did know him who happens to be reading.