15. The system of claim 13 , wherein adding the particular users to the first group further comprises: determining that a second group of one or more of the plurality of users have respective likeness scores that satisfy the threshold after removal of the author from the first group; and adding the second group of users to the first group of users such that each user of the second group is permitted to send anonymous messages through a respective account to the first user.
13. The system of claim 12 , wherein the operations further comprise: after removal of the author from the first group, determining respective likeness scores of one or more particular users in relation to the first user and, based thereon, adding the particular users to the first group or removing the particular users from the first group.