There's two things wrong with it:
1. A good agent for one is not always a good agent for another. The best agent in the entire world at selling non-fiction might not be great at selling the next Harry Potter novel.
2. Many people are looking for comments inside of the threads dedicated to the agent or agency -- so good comments should be placed in those threads.
So, I would worry that having a kudos thread might keep people from spreading the word inside of those threads -- and I think it is far more important to have them there then seperated on a different thread where people looking for information on a specific agent might not look.
