See PHI505. An install would like a feature which I bargained down to a `!history` command that replays an object over email, for reviewing events if you were `@mentioned` onto something you don't have context on and are off-VPN on your phone on a train. Perhaps see also T11934.
See PHI531. An install would like a way to abort builds for older diffs when a revision is updated. There's some consideration for adding an "Outdated" status vs "Aborted", but this is probably a larger problem which overlaps with PHI533 (timeout "Waiting for Message" builds), run command timeouts, etc.