The next version will have an option to say, don't show to users with less than x posts.
If you already want to use this, because maybe you don't want to show it to long term members, the second block in the list has a conditional llike this
<xen:if is="!{$isAwaitingEmailConfirmation} AND {$visitor.user_id}">
replace it with this
<xen:if is="!{$isAwaitingEmailConfirmation} AND {$visitor.user_id} AND {$visitor.message_count} < 5">
The number 5 at the end means, users with 1,2,3,4 posts will see it, 5 or more, won't.
The benefit: dont' bother long term users, limit it to newbs with no posts.