Yup you're totally right. All these ideas really seemed like things that would trend on HN (but that's easy to say in retrospect, getting to the front page isn't quite so easy!).

> My final advice for seeing how online services validate their ideas - run the product's domain through a backlink checker. It lets you see what other websites link to their product and what avenues they pursued for outreach. Each of those submissions exposes the product to potential customers and gives valuable feedback to the creator.

This is one thing I know I'm terrible at. I barely use any SEO tools properly, I should probably just hurry up and pay for ahrefs or whatever already.

I don't think the concept of checking backlinks even clicked properly in my head until I read your explanation, thank you very much.