I'm glad you've noticed that HN is relatively spam-free. If you continue to read HN, you'll also notice that we don't ban people for replying to us. We ban them for breaking the site guidelines, and even then we're pretty lenient.
It's not spam when a longtime user is linking to their work in a relevant context and hasn't been making a habit of it. The two cases are trivial to tell apart if you're willing to take a minute, and it has always been ok to for users to tell others about their work this way on HN—as long as they don't overdo it. Whether you like the project or not is a separate question. As for thoughtfulness, "spam your scam elsewhere" is basically leading with a punch in the nose.