The Report Abuse module features a two step process to ensure that use of offensive language or refusal to meet transaction obligations (e.g: constantly declining to ship purchased items) is dealt with as quickly as possible. First, leave negative feedback, to warn other users to avoid a particular seller/buyer. Second, inform the admin by sending a message via the Report Abuse button.

For reporting a user go to one of his/hers listings and select Report Abuse:

Next, complete the form indicating the reasons:

The message will be displayed in the sender's Inbox (Home -> Members Area -> Messages -> Sent):

and in the Admin Interface (Tools -> Messaging):