Excellent suggestions, Pablo The Devil!
To the original author of this post:
That's precisely what the stars are for... just make it so users can't rate each other and only you can. Then post something saying such users are valuable and high quality folks and it's "an honor" to get a 5 star rating and "must be earned."
You can also could setup a special private forum for those users, and make it clear to everyone else it's a special forum! Something they need to earn to get access to by helping others.
Do **** like this and you'll have users begging for access...and they'll be stepping over each other to get the recognition. Humans are funny this way... they'll do nearly anything to be apart from the crowd in a positive way.
