I see the appeal, and I think I agree. I’ve read posts that I particularly liked, that impressed or informed or amused me, and it’d be nice to show the poster some love and appreciation without cluttering up the thread with contentless posts. But on the other hand, it would make the boards more cluttered. (Is there a way we could set a user option to hide the Likes if we didn’t want to see them?)
Anyway, here’s one thread where this was discussed before: Why No “Like” Button? As you can see, not everyone’s crazy about the idea.