Where, exactly? His Twitter feed contains a single link to each of his original Apply HN and the later poll (plus one link-less joke about the poll). I mean, yes, he has a big following, and yes, he promoted his application (which everyone involved admits he would not have done if he had thought it was against the rules). But "explicit and repeated" makes it sound like a lot more than one (humorous) tweet per poll.

And it's not like he used a personal account, either. That one doesn't mention it at all. It's just @Pinboard - and frankly, it would be weird if you didn't think current customers would want to support you in growing your business.