@meta When I tried to sign up only using my ORCID I got a 'something went wrong' error message from the instance. But when I signed up with my email and clicked on add ORCID everything worked instantly (as I had already granted the permissions to the instance).
@twm I believe this might be by design ( @mayel may correct me if I'm wrong). At this stage, signups are by invitation only, and IMHO, it makes sense that it is not possible to create an account simply by using ORCID's API.
I'm not so sure what to expect if the signup was open, though. Creating an account with your orcid number instead of using your email may be interesting, but I do not know if having an email would be better if you want to receive notifications (by the way, I don't receive any, which makes me wonder if we have the configured well the smpt server or bonfire is very respectful in that matter -I would not be surprised about this) or reset password.
What is really cool, though, is that you can definitely sign in with orcid, and how it populates some data into your profile.