How To Change Your Primary Group To Authors?
Wing likes penguins
1st, before the levels were introduced, changing your display group would give you a custom border around your pfp on the forum. This has been disabled for a while now.
2nd, on your chapters, down at the 'about author' section, you have a custom image below your pfp. This is the only visible feature related to having a different display group, that I'm aware of.
This is how mine looks. I joined the WriTE group 3-ish years ago and it's set as my display group.