Exactly. Click = upvote. Returning to SERP after a short dwell time = downvote. It's noisy but because you can mine such things implicitly by just logging user'

Exactly. Click = upvote. Returning to SERP after a short dwell time = downvote. It's noisy but because you can mine such things implicitly by just logging user's behavior, the volume of data is way bigger than what an explicit feedback system can provide.