Thanks for the link @julian. I was asking myself why like 90% of forum users don't have the badge showing up. My first thought was that they didn't like it, but that all these users instantly changed their setting to show no group title seemed a bit unrealistic.
Now I know that the answer is just that they edited their profile once (profile picture e.g.) without being assigned to a group at that time and now the "no group title" setting is saved forever. I really hope this can be updated because it makes the reward system some kind of pointless. Normal behaviour in my view should be that every new group assignment (User with 50 posts, with 100 posts, etc.) should be assigned automatically.
I would even say that the "show no group title" should be an additional setting without being part of the group title listing. The users don't even know that they saved this setting when they edited their profile once.