I think a little bit of phone user experience optimisation when tagging users. That function misbehaves often on a phone and tagged names usually cannot be deleted. Maybe quick tips section for new users including some key navigation points. Or maybe a short intro video for new users made by you?  A button "Privatise" in journal section that will lock the journal from ability to comment but can still be modded if the user shit talks about other members. OR The ability for journal owner to delete comments from other users.