Frustrated by their Google searches, people are funneling their queries to a site that isn’t a search engine at all: Reddit. Earlier this month, that included me. Reddit, which went public in March, is a social network with 82.7 million daily active users who gather and usually post anonymously in groups called subreddits. Users can “upvote” or “downvote” what others contribute, surfacing what are considered the best responses. The decision to turn to Reddit is happening because many...