I always feel weird when I add a tiny bit of salt on to watermelon, I've been to friend's BBQ and everyone looks all weird at me. So far I think it's a "Chinese" thing to do. I usually add some salt to watermelon, except when we're eating the yellow varieties "Xiao Yue" or "Siu Yoke". Theres something about the flavor of the yellow varieties that I can't seem to add salt to it. As for the Salted Plum Powder, I see that as a "Taiwanese" thing (my mom's Cantonese, dad's Taiwanese). Everytime we goto the night market in Taiwan and buy fruit, salted plum powder is thrown on the side with watermelon like ketchup is to french fries. As for brining pineapple), I think the foremost reason is to remove the acidic "bite".