@artpoetryfiction Vivaldi offers a blogging service as well. The blogging platform uses WordPress and you most likely found yourself on the WordPress dashboard.
Also, we're working towards a single sign on option, but to implement that a few other puzzle pieces need to be put in place first. For now, if you're logged in on the Forum or Vivaldi.net, it should be enough to just click Log in on the other page, no need to enter the login credentials twice.