One way this could be done is by mimicking the “summarize topic” function.
Comments submitted by “experts” (users whom you have added to a specific group) will have their comments displayed, while other users will have their comments snipped with a message such as: 5 posts hidden.
The functionality would be almost identical to the current “summarize topic” feature; the only difference would be the criteria by which posts are hidden, and that the feature should always be invoked rather than only when a reader specifies.
(If you don’t know what feature I’m talking about, have a look at this topic.)