Documented here (and the next few posts): Login to your account - What the Daily WTF?
Circumstances leading to the apparent issue:
- Add a group to a user
- Make the primary group of that user that group
- Remove that group from the user
a) note that on the admin screen, the user no longer has a primary group (apparently correctly removed)
b) post jsons however retain the old group as the primary:
I don’t have a primary group and I’m no longer a member of bots: