Yeah, but if you look at his submissions, comments and account lifespan you can see he has no interest in taking part in the community, only pimping his app.
Clearly he knows about HN. Possibly he was lurking. Maybe he's not sure or is not confident enough to comment often. What he has done is created an app and a few interesting blog posts. As far as I'm concerned, that is what HN is all about!
I've been lurking on HN for 4+ years, and I rarely ever contributed comments, mostly just read articles and read the comments to see others opinions.
Don't think this is true? Take a look at how many comments are left on articles on the front page, then if you were lucky enough to reach the front page of HN, take a look at your analytics software. You'll see something like 20k visits in a short period of time, there's no where near that number of comments. Most people passively participate in this community.