good thing it wasnโt (source: i was the third party recipient of those shared DMs; they were fully irrelevant to admin/mod action, abusive or otherwise)
How so? On Lemmy, at least, they are absolutely not private. It is just a way for two users to communicate without cluttering up a thread or something. Not a way to communicate in secret.
EDIT: Oh, I missed the joke. DM = Dick Move. Woosh
It's private in the sense that the DMs were made between 2 people. They are public in the sense that the admins of the instance(s) can read the DMs. Just like admins of any server can read anything that's not encrypted at source.