About risk profile:
- Mastodon is like email because you can't delete federated toots
- Mastodon is like twitter in that Google's search bots index it, unless your admins robot.txt it away
- Mastodon is like being a teenager because the people that own your instance can see all your private stuff
Have a talk with your admin about their policies.
By default, assume everyone will be able to read your toots forever.