Has there been any discussion around having a negative merit thing? Like something that costs 100 merit to deliver 1 stab or something. Obviously there are tools like the trust system, but the focus of the trust system is on fraud or at least trust worthy behavior. Someone can be not untrustworthy but still be deserving of a swift kick in the groin.
The trolls you are talking about are quite persistent, that is their way of life. At some point, the community will lose interest in ripping them off, while the trolls will continue their story again and again with the same intensity. At some point, the community will lose interest in kicking such people in the groin, while the trolls will continue their story again and again with the same intensity.
You can't beat idiots on their turf.