Reddit reviews Heidegger, Art, and Postmodernity

That's a bit tough, seeing as postmodernism itself took a number of forms throughout philosophy, literature, film, art and so on. The only place I've actually seen discussion of post-postmodernism is with David Foster Wallace and his fiction, generally understood as intending to push irony to it's breaking point and get us to try and rediscover some more sincere and genuine way of feeling and existing (this is sometimes referred to as new sincerity, although this term itself has had a somewhat mixed reception). I've not heard of post-postmodernism in philosophy, although Iain Thomson's book Heidegger, Art and Postmodernity does make an attempt to use Heidegger's thought to "think through" the problems of modernism and late-modernism to a genuine and sustainable postmodernism, so that might be worth looking into.