If you blink you'll miss it. We're rolling out a new feature today on the site, giving you yet another way of interacting with our authors. You can officially annotate text paragraph by paragraph. It's like image annotations but for words. In case you're still confused you can find the full instructions here.
You could always go the traditional route of quoting an article and typing your response underneath it in the discussions below each post, or you can just let Kinja do that automatically for you. Use your newfound powers wisely, friends.