User blog comment:DaNASCAT/Technical Update: March 7, 2016/@comment-25739558-20160308125907/@comment-126761-20160308130304

This is related to a general rework of the rights system code - which is generally supposed to be an invisible update (apart from the changes already mentioned in the notes above).

Anon editing certainly still exists - I'll check into why some group visibility (on ListGroupRights) has changed.