It's from a text from a friend who knew him, if that matters. We all got PhDs from the same school. I have been here for 6.8 years and in the last two I find myself going back to Slashdot more and more.
Your first comment didn't say anything about having a personal connection or any first-hand knowledge of the situation, so it was reasonable for people to consider the comment as empty, insensitive speculation.
There are valid grounds for wishing that HN was better than it is, but this case doesn't epitomise anything that is fundamentally wrong with HN; you could have done better in your initial comment, and then done better than to use it as an opportunity to take a swipe at the entire community.
For HN to be better, it relies on all of us to do our bit to make it better.
I wonder if you're running into the problem of mixed cultural standards on HN. People here come from very different backgrounds but we interpret each other's statements without knowing that—a hard problem. I'm not assuming anything about you but I can imagine different pairs of backgrounds that would react quite differently to the simple, blunt question "was it suicide". Some would think "what's the problem it's a simple factual question" while others would wince and almost feel pain. This isn't an issue of PCness, but of the lossiness of channels across multiple cultures.
Different cultures also have different standards around speech vs. writing for such a question, as well as around public vs. private. And a small private conversation and a large public internet forum are miles apart even before bringing culture into it.
On HN we're dealing with all that and more. Our way is to try to have a local culture in which people err on the side of posting thoughtful, substantive comments. These two factors—considerateness for others and solid information—compensate for packet loss in the channels, making it easier for real communication to occur, leading to more interesting conversations. But it comes at a cost: utterances can't be quite as sharp or colorful. We give up some expressive range. Things get more bland. It took me years to reconcile myself to this—I hate blandness and am a fan of the historical art of barbed wit—but eventually I realized that if you don't make this tradeoff then the smart people eventually leave, and that would be blander to say the least.
People do sometimes mistake this approach for political correctness—and then wonder how the author of "What You Can't Say" could have created both—but that's because they don't understand what HN is going for. (I feel annoyed sometimes when people accuse us of being champions of bourgeois politesse when they haven't the least idea, but what can you do.) We're trying to optimize the site for interestingness—intellectual curiosity. The HN guidelines are an engineering tradeoff to achieve a design goal: one we have to make to protect HN from the dynamics that make internet forums less interesting and then dead. This design decision goes back to the founding of the site: see https://news.ycombinator.com/newswelcome.html and https://news.ycombinator.com/hackernews.html.
If you don't want to put some effort in writing a substantive comment, probably you should go back to Slashdot. Your first comment showed no effort in justifying your speculation with relevant evidence. The reason why I like HN so much and why I gave up Slashdot and Reddit in favor of HN is how I don't have to scroll down a list of funny or low-effort comments to find a few substantively written comments. The low funny-to-substantive ratio of HN is what attracts me to HN and I am glad that low-effort comments like yours are quickly downvoted.