I had deployment training yesterday, and the EM of the deployment team asked me to please make sure my team monitors for errors in production post-deployment. This could be an addition to the definition of done for new features.
Topic on Talk:Abstract Wikipedia team/Phabricator style guide
Yeah, this one's a tricky one; we don't deploy individual patches or features (except for backports), so with the current model that responsibility (generally on my shoulders as tech lead) doesn't tie back to the individual tasks.
Once we've launched into production, I'd not be keen to have all the tasks we've worked on just sitting around for up to a week each time, waiting for production QA sign-off, but maybe we could have a column for that? (It'd need us to scrap having the phase milestones, as you can't have both.)