Hm, thanks for sharing this. But my sense is that it makes things more complicated rather than simpler. It’s much easier to explain: “… and when you’re logged in, you just need to go to groups, find group xyz and click <whatever it says on the button>” than making them change emails. And more fail-proof too.
But although that is easier, there are still enough people around for whom “go to groups, find group xyz” constitutes a significant challenge.
Couldn’t find any previous topic when I searched earlier… But I’ll convert this topic into a feature request and we’ll see.
I didn’t even dare to think beyond the one-token-per-new-user principle, I was still assuming separate tokens for each invitee, but yes, a single token would to the trick for me too.