I think the three distinct ratings are useful. While a single rating is fine for individual posts, it does not help much in determining what kind of poster the user is as a whole, as it is here:
If there was only one rating, we would not be able to distinguish between users who write lots of helpful posts to users who write lots of funny posts, or if they do a mix of both. These three ratings, when viewed from the user profile, provide a suitably diverse rating of the user, and does not blur the reasons they were up-rated (quality, helpfulness and humour being the three main categories here).
Perhaps.
I just find the whole 'thanks' and 'laughs' part so subjective. So are 'likes', sure, but at least you can imagine a broad spectrum for which someone liked the post. Seeing that someone has a lot of 'laugh' ratings, and then finding their posts completely unfunny, for me that would make the ratings suspect and hard to believe the next time I saw something like that.
Same with helpful posts. There are so many naive problem solvers out there (like those of us in this topic, hey-o!) who produce suggestions and tips that aren't really all that helpful. Except, to the OP, they may just be considered helpful, or at least they
sound helpful. When someone with real knowledge in that field comes along, then, and sees all the 'thanks' ratings on a post that is completely off-base, it also makes such ratings suspect.
This kind of thing shields users from true and accurate evaluation by masking their posts with 'likes' and 'thanks' and 'laughs' from people who may or may not actually get the intent behind the post, or who naively believe the post was helpful. I know we're in a society of instant gratification, of 'click and move on', and so forth, but this
is a writing community. Having ratings such as these which trend towards simple categorization of a person, rather than writing out a thoughtful response, is kind of defeating the point of this community. Which is why, if we must have some form of rating, let's make it as simple as possible.
tl;dr: I think there's too much subjectivity in the specific ratings to base generalized opinions of a person on those ratings alone, and makes it a poor argument for having three ratings.