I had never noticed that before. Can you rate a post or just a thread?There is, in the red header, the "Rate Thread".
that is correct the whole thread not just a post on it. I don't think many people pay much attention to the rating anyway unless someone with too much time on their hands starts rating every single thread in all the sections like a person in the past did.
You can give a thumbs up by adding a post in the thread to thank the person that helped. Then other people reading the thread will know that a solution worked for someone.