I always grind the ax that I really want #Mastodon / #Fediverse users to be informed about how insecure this whole system is from its foundation.
DMs is a big element of that.
You mention messaging that isn't encrypted, but in this system the security goes the other way: not only is it unencrypted but it's basically just another public post with the suggested audience of a single person.
I really hope users realize that DMs have zero guarantee of privacy.
Absolutely, I don't expect anyone to understand ActivityPub :)
But I DO think UI designers, folks at the Mastodon level, need to make sure users know that anything they send over DM carries no privacy guarantee.
They do make some efforts in the interface to convey that, but I don't think they do enough, considering how often I interact with users who don't aren't aware of this factor.