I recommend disabling presence in !error in both the default configuration and upgrade scripts.
insert into SAKAI_SITE_PROPERTY values ('!error', 'display-users-present', 'false');
It's not a good idea to show users the names of other users, except in their own site. While probably not technically a FERPA violation, because other users can't tell much about them, some universities allow students to hide themselves completely for cases like stalking. So it's really a bad idea to show the names of other users who are online.