I think this’d be pretty easy to implement in the plugin I’m (still) planning on making removing that metadata from all emails, in a way that enables you to just turn this on for staged users:
@tobiaseigen I don’t expect to get to it for at least a couple of weeks, but if you want to know as soon as I do you can track our internal ticket about it: https://github.com/mozilla/discourse/issues/51
I’ll also be sure to post here when I’m done.