I work at Discourse. As a regular user, if you want to prevent these new user badges (and notifications), head to /u/yourusername/preferences/interface and check "Skip new user onboarding tips and badges".

It is in our plans to eventually rework how this new user education and notification system works, and I suppose eventually with https://id.discourse.com/ the intent would be that your preferences follow you to every Discourse site you sign up for, so you could just set it once.

As an admin, badges can be disabled entirely, or individually.