Thanks for sharing the article and the feedback!

Community curation is a good concept. I'm a little hesitant because community contributions can degrade a platform (e.g. people writing marketing content on Wikipedia). But the biggest hurdle had been building a reasonable content index, so despite that risk, the reward will seem to be worth it.

Re ranking: what you're saying makes a lot of sense in the context of topic discovery. But is less useful for q/a or reference style searches. Although it will still probably be good enough.