I feel like Reddit is a bad example for an argument against search, because it still relies heavily on search. People aren't finding a specific subreddit for their query and then browsing it until they find what they're looking for, and they're usually not even searching directly on Reddit (because of the poor search quality), they're searching on Google.
What does "manual curation" mean in this context? I think it really just means "absence of spam/low quality content", which manual curation is not strictly necessary for.
Yahoo, back in the days before Google, was a manually curated search engine. They had a team of people doing the indexing work and creating the database from which the search engine pulled results. In principle, this avoids SEO spam because the manual curators aren't going to add spam sites to the index. Reddit functions similarly because, in principle, users aren't going to upvote spam posts.
What does "manual curation" mean in this context? I think it really just means "absence of spam/low quality content", which manual curation is not strictly necessary for.