I'm seeing people on twitter saying admins can read all your DMs on mastodon.
This isn't true, we only see a DM if a person in the DM group that's allowed to see it reports it.
Then, like any report, it shows up in the moderation panel, just like it would for twitter moderators.
Otherwise, it won't show up, as shown here.

BUT. No, DMs aren't a fully private end to end encrypted system, don't consider it as such.
But no it's not just an open thing for all to see on your admin team either.