I think the practice of using subdomains for each function of backdropcms.org is creating a usability issue in the form of the number of separate logins required.
Since being involved, I have had to create separate accounts at survey, events and forum. Assuming people engaged with Backdrop may engage in all these ways, I would suggest having them all under the main domain could simplify matters for members.
Normally using the same login credentials for multiple sites isn't a good idea, but since we're working towards a single sign-on solution for all Backdrop sites, I figure it's ok.
I've therefore setup the same username & password for myself for all Backdrop sites. And since I've saved each login in my browser, I now have my own poor-man's SSO solution for Backdrop 😁
At least until one of these is implemented: