A quite frankly brilliant concept design for a "Mea Culpa feature" on Twitter. The idea: let users add a flag to their own tweets admitting mistake:

Adding a "mistake" notice would trigger the tweet to reappear in people's timelines that already saw it, helping the "retraction" gain ground, and stop new users from liking or commenting, de-amplifying the message. Nick also puts forward a suggestion for a "forgive" interaction that would appear under tweets with Mea Culpa notes applied, so that users can receive positive reinforcement as well. I think it's all great and a fantastic idea for humanising social media, building a UX that drives more positive discourse and more civil interactions.