15·1 year ago- It is not unsafe.
- It is not 100% private. Admins can read your messages if they choose to investigate your messages.
- It will not get blasted out to the whole fediverse; just to the recipient you indicated. (Unless an admin from the previous point reads your message and publishes it publicly on the fediverse)
- You do not get to do anything naughty with it; expect to be caught if you break the rules.