This is a warning, perhaps a request for an update to the card system.
It is possible to buy one's own cards at auction, as in placing a bid that matches a sell offer that one has made.
It seems that the system does not recognize that the user is attempting to buy their own card placed on auction. I suspect that exists to allow puppets and the like access to the market. Perhaps, as a precaution, the system could be updated to prevent users from doing that? But I suppose that's what experiments like this are for.
