The reason for suggesting that a member be able to "rate" the thread multiple times is valid, I think, because the thread changes with each post.
A well conceived initial post can deteriorate into drivel.
A mediocre threat might take on a new vibrant life.
I don't mind that you don't agree with me, at this time.
Perhaps you might change your evaluation of even this thread when others add different ideas that you might like a lot more than mine.
Should you then have an opportunity to re-evaluate, or should you be stuck with your orignial assessment of a completely different series of posts?
As far as a rating system, with nothing happening as a result, what is the point of voting if it doesn't change the status quo?
Members will only vote if their votes effect change, one way or the other.