.... unsolicited PM spam to buy or sell accounts will lead to your account getting banned anyway if the messages are reported, but those interested in buying accounts obviously wont report them.
What I wanted to convey was: people will fear making a buy request via PM due to the possibility that the message receiver would report the PM to staff and the person making the offer would get banned. (Unless the receiver is also willing to make the deal, so there's 50-50 risk factor for the person making the offer)