The best channel for that is messaging on the marketplace. I think the benefit of quarantining the newbs is that by the time they earn the privilege to post in vendor review threads, they'll be able to write higher quality reviews, and they'll have some posting history on which others can judge them, as opposed to all the shill accounts that pop up now. And I realize that they are spamming their way to 50 posts, but realistically that means they still have to spend a few hours on the forum, in which time they'll learn the ropes, at least a little.