One could always make a threaded comment section on a project and call one thread offtopic or whatever.
Developers that want to get contacted will find a way. Most that want to interact with their audience on that personal a level set up a discord.
A direct or private message feature is more suitable for interaction between users on an equal footing. Like from player to player. Itch does not have this kind of social media feature. You do not find "friends" on itch. And while some developers would be glad for feedback (for specific projects at least), I would guess most do not want to get contacted or they would have set up dedicated channels for that.
I believe the reason behind this lack of friend gaming experience, compared to Steam, is the scarcity of actual multiplayer games in the indie sector. Small time studios and single devs just have not the capacity to implement such features. Steam got big basically with Counterstrike and providing an infra structure for people to play toghers games like this, was essential.