Selling merit isn't allowed (wasn't created for that purpose) so anyone that proposes to sell some will be red-tagged by DT members. It should limit possibilities as new accounts don't have merit to sell, and older ones wouldn't risk to red-flag their account.
Only remains the hacked or sold accounts...
This. Furthermore, these merit sellers need to have a source of merit, once all of the initial distributed sMerit is used up then they will really struggle to have much merit to sell. Even if it continues it will be a drop in the ocean in terms of accounts that can buy ranks, given how scarce sMerit is.