I actually built an IRC bot that did this once. It searched reddit for your question, took the first result, and posted the top comment. It worked very well for certain kinds of questions. Especially if it came from the better subreddits like askscience, but even just reddit in general.

I improved on it a lot with a whitelist of subreddits and some machine learning to select the best thread. But I was only touching on what is possible with that data.

The scope of the discussions on reddit is huge. Despite a lot of jokes in the comments here, the quality of the comments on average, is pretty decent. And the metadata like subreddit and score are extremely useful for filtering it down more.