Does it really matter?
So what if people are one post wonders, as has been said it's up to the 2 parties involved as to whether they want to do the transaction or not.
If a CA regular has some extra tickets to sell then they can choose to contact the One Post Wonder or not. and Vice Versa if the OPW has tickets to sell.
It could be said that we are helping fellow LM fans by selling them tickets at face value, and isn't that what CA is about???
Ok, it can be annoying if the OPW buys from a CA Regular at face value and then sells them on at a profit, but thats the way of the world! The CA Regular will have got his/her money back, so should be happy as thats what they wanted!
I'm sure it would be possible to exclude OPW's from SoS but then they'd just end up posting in one of the other sections anyway...