That's partially why I sped up work on merit. I don't agree with using the trust system for pure spam; that's not what it was designed for.
Maybe you can rename the "trust" in something "concluded deals"?
Just adding "trading" in front of trust should be enough for trust to be only for trades. Also, everything else can remain the same with the trusted and untrusted feedback.
"Concluded deals" somehow seems like it's only for successful deals and that would be ok if ones (who would otherwise get negative trust) get banned instead.