I have to go against the grain and disagree. I think that adding non-voting "emotion" responses would be too complicated, detracting from the beautiful simplicity of what we have going on here. "Likes" are pretty much empty anyway - if one wants to react emotionally to a post, why not leave a comment?
RE: Proposal for reactions feature: separating structured user opinion (both positive and negative) from reward-modifying upvotes/downvotes