Hacker News is an online community. It has a pretty open membership policy, which is that, if you show up here over a period of time, and manage to not get hell-banned, you're a part of the community. Congrats!
Part of being in a community is that it's pretty common to have a kinship with other people in that community. This place isn't a real-life place, so naturally, that kinship might not develop as quickly, or spread as deeply as one might in person. But you'd be surprised that it can still develop.
So, "the vast majority of HN users" might not actually know who raganwald is, but I'd bet they've probably seen at least a few of his comments, at least if they've spent any amount of time here. However, "the vast majority of HN users" aren't actually the community. There's nothing stopping them from being part of it, they just aren't. Which is fine (I don't consider myself to be, for what it's worth).
But when someone who is a part of the community has something good happen to them that's of interest to the community, people share it.
The fact that this story is popular is a triumph of community, not a shitty side-effect of this place not operating the way you wish it did. I hope it continues to feel this way, lest it really turn into a shitty link aggregator that you so wish it were.