It is a perfectly adequate paper trail. It's much easier to check in a postmortem than shouting something across the desk. Like code review, because you know your approval will be recorded irrevocably, you just think it through that little bit extra before approving.
Well, you can undo your own reactions, so not 'irrevocably'.
We typically do something similar in Hipchat - "Hey, I'm about to push to prod, any objections?" "No, go for it."