As part of efforts to improve user onboarding, I shipped an experiment to a subset of new users showing them a Getting Started page immediately after signup to help them get to what we think are some of the most important actions for new users to take. We compared the subset of users against a control group to see whether such an experience improved engagement over a period of time.
Last week we shipped outdated comments...well, brought them back, actually. We used to show collapsed comments on outdated diffs as a single line, but removed that when we shipped code review recently. We brought that back last week with an improvement: you can now toggle open threads on outdated diffs in a review individually.