Fine, I'll be helpful, since I'm so nice (but you could probably tell that from my post count 
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The reason for this is that somebody with several thousand posts is clearly not a huge troll, or they would have been permabanned by now, or at least learnt a lesson from their bans. The exception is if they have negative VG$. Thus, if they say something controversial, it can be dismissed as a joke, or a one-off.
People with low post counts do not have that luxury. People are not used to seeing them post, so if they make a fanboyish/troll post, people could think that is their regular posting style and call them out on it. If, before Rol become famous, somebody with 100 posts made a Rol thread, do you think he would possibly avoid a ban? It was because Rol's threads were so uncharacteristic that they were hilarious, and never ended up getting him moderations.
(Former) Lead Moderator and (Eternal) VGC Detective 
