HN in general has a very strict policy against what "people find interesting":
On-Topic: Anything that good hackers would find interesting. That includes more than hacking and startups. If you had to reduce it to a sentence, the answer might be: anything that gratifies one's intellectual curiosity.
Off-Topic: Most stories about politics, or crime, or sports, or celebrities, unless they're evidence of some interesting new phenomenon. Videos of pratfalls or disasters, or cute animal pictures. If they'd cover it on TV news, it's probably off-topic.
News are like addiction, people don't act in their own best interest, they upvote things that they don't really want to see.Also "just flag it" is not "wasting moderator's time", but the recommended procedure:
Please don't complain that a submission is inappropriate. If a story is spam or off-topic, flag it.