I understand where you're coming from but in this case, it is irrelevant; as a result of the service that the vendor is providing here, it means that all business could be completed via TorChat if he provides a means by which buyers can contact him and engage in instant transactions. That is strictly not permitted. Backup communication means may be provided as a backup in case of a long term site outage - they may not be used so as customers can contact a vendor to arrange a transaction. All of that MUST be done through the Silk Road messaging system or the Shopping Cart. Libertas