[EnderShadow8]

Instead of using upvotes from sites such as Reddit and HN, why not instead allow the users of the search engine itself upvote and downvote results? This might allow quality results outside the scope of larger online communities to still be highly ranked, and also tailor the results to the audience of the search engine itself.

[Gigachad]

Because then instead of SEO you have upvote farms and paying people to upvote your links.

[colordrops]

What about it just considering your upvotes only and using them as inputs to a recommendation algorithm?