While I don't want Cohost to have a DM system, I do wish it had something similar to a Guest Book, or perhaps FurAffinity's public shout box, where you can leave public comments on someone's profile. There's been many instances where I've wanted to ask someone about where their profile pic is from, or just to leave a positive message. It feels like the only way to do that is to piggyback off of an existing post the person has made, which feels awkward.
Any such system would need to have the usual opt outs and ways of tidying/locking it to avoid abuse, but I feel like such a system would be a positive alternative to DMs.