It would be nice if users who've declared their age as 18+ could click a box or choose from a dropdown or something to make that post only visible to users who have also declared their age as 18+.
i'd like to be able to blog about parts of my life that are heavier/more serious/focus on adult spaces and would feel wildly uncomfortable doing so with the knowledge minors could freely view and engage with those posts.
the vice versa could also be helpful, with users who've declared themselves as minors being able to make certain blog posts only visible to other minors.