Kale and other leafy greens greatly benefit from a nice massage before you mix them in a salad. But if kale's bitter flavour bothers your taste buds, you might want to change the usual order of operations.
In this video from the Wired YouTube channel, Dan Souza from Cook's Science and America's Test Kitchen adds a twist to the ol' "massage your kale" trick. Instead of rinsing your leafy greens before massaging and chopping, you should rinse them after. Why? The massaging helps soften up kale, but that and the cutting release a bunch of bitter compounds that don't taste too great. But if you save the rinsing for later, you can wash away most of the bitter stuff that gets released. Now you won't have to overdress your kale salad and undo any of the health benefits.