Maybe it's a result of years of FB, twitter and even myspace, but a comment feels the most rewarding. It's easy to like, even zap, but it takes effort to type something, and that feels real. Even someone typing cool, or polite disagreement with reason explained is better than a like. I say this from arranging Assange vigils. A like is support sure, great for motivation, but a comment, hell that might even mean actually coming down and joining, My rule was I'd trade 10 likes for a comment.