I've paused more than once trying to decide if I was going to circledot a comment or a post, and working through the rationale of doing so. That doesn't happen with likes. I'd argue that the approve/like/share tension actually promotes thoughtfulness of interaction. Of course, this is the internet, so consequence is always both great and small, but the fact that we feel some is probably not a bad thing. I would expect a separate like button to moslty encourage mindless exercise.
Funny thing, if I make a trite comment that is heavily spoked, I feel a bit guilty, and a solid contribution feels like atonement.