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.

Ah. But we're still using some algorithm that's doing curation to even look at reddit. I see you're point about reddit being manually curated via upvotes, interaction, and moderation, but there still has to be something in between to even find the content and match it with what we're looking for. Even reddit's too big to just be a page of links, a la Yahoo.

Reddit has avoided

Because they want a bias-filtered selection of the internet. It is very obvious looking at the reddit comments that most are made by bots and not humans, the difference is that most behave similarly and the upvoting favors sameness.