I am not sure what you mean by rating service. The rating field in Link Library is a data field in the Link Editor that allows site administrators to rate links. Visiting users are not currently able to make changed to this rating. Perhaps down the road.
Thanks for your support,
only the administrator can rate the link in the library?
Maybe this is an incentive for the next update, which also visitors can rate the links?
+1 for this idea.
Having users rate the links would be a nice feature.
Once Link Library 6.0 is stable, I think this will be the first new functionality I work on.