I'm with you on this. Not only am I confused about the Hacker News component of this story, I'm confused about the "news" component of this story. If he was, say, a politician married to a woman who had voted against every law recognizing homosexuals as equal members of society, this would be news albeit not hacker news.
As it is, it simply isn't newsworthy. It might be titillating or perhaps surprising to people who bothered to hang the wrong label around his neck. That's about it.
It's important for him to mention in that he is 81 years old and is probably contemplating a shorter future than any of us. It's a good thing for him to tell everyone rather than have it wind up in post-mortem articles that make it out to be some dark secret that could be used to cast his life's work in a bad light.
I agree with your suggestion that he ought to have written this post. I also suggest that there are many types of blog posts that ought to be written. That doesn't mean they ought to be on the front page of Hacker News.
People voted to put it there. I've submitted things that people haven't voted on at all, which surprised me, but that's how it goes. Some things get votes, some things don't.
As it is, it simply isn't newsworthy. It might be titillating or perhaps surprising to people who bothered to hang the wrong label around his neck. That's about it.