And yeah I don't think it should be complicated why Cohost has no DM system... it's a huge moderation burden, hell it's an extra regulatory burden, I think, especially if you did it in a reasonably secure way (as, I think, users would expect) where your DMs aren't just plaintext visible to the site's admins. Cohost is made by like four people. C'mon do the math.
platforms that are trying to be public spaces, of one kind or another, never needed DMs
corporate platforms had a strong incentive to normalize the expectation that platforms have their own DMs, because prior to that everyone was using instant messaging services alongside the other stuff, and that meant the large-group platforms made less money
because when the messaging was unrelated, people weren't dependent on the social media site to talk to their friends. when all kinds of communication are bundled together under a single umbrella, we ARE dependent on platforms, even if we try not to be, because there's always gonna be someone we care about who refuses to learn anything else. that's where the so-called network effect gets its strength.
quite aside from the questions that arise in a modern context about how to balance the harassment potential and so on, we should never have wanted that bundling in the first place
Cohost lets people list as many alternate contact methods as we choose - including none. it's not only that that's by far simpler right now, we also think it's the right way to handle this in the long run.