@avuko @mattblaze That's what they are. They're meant to alert someone, and should be called that - Toot Alerts. They are not private - they are toots directed to the recipient with a patina of privacy.
Nothing here is truly private. If it's not encrypted, and resides in databases - 2 at least for every cross-server toot - in unencrypted form, it's public to at least every system administrator with access to the database(s), whether they are involved with the Fediverse or not.
Then there is the issue of a follower noticing a "private" thread and jumping in.
People who want privacy are best served by Signal at the moment.