Actually I think it's a good thing to let a mod know a deal has gone sour. This should only be done once with the knowledge that you are only notifying them of the problem, nothing should be expected of the moderator. This way the people who run and control this site would know if they have a bad egg on the site.
What I can't understand, what's the difference between a trade or a sale? Both transactions can go bad.
The problem is Moderators can't do anything about a "bad" trader. We aren't going to investigate every bad trade, double check and verify all tracking information, and we have no way of knowing exactly what was greed upon by the traders.
Yes, people PM me with concerns about trades gone awry, taking a long time, or when they've been flat out ripped off. I feel bad for anyone who has been on the bad end of a trade (it's happened to me three times), but it's going to happen, and everyone has to decide if any and all trades are worth the risk to them. I even added a pinned Trading Guidelines post to the Trade/Wanted sections to make it perfectly clear that trading is a risk, so there's not much more I can add.
My personal preference would be for each member who keep a list in the "Good Traders" post to add a "PM me before you consider trading with __________ ___________ " to their list. It gets the point across, or at least should.
The way I look at it, the Trade/Wanted sections here are a bonus for all of us. I'm glad we have them and hope we always do, but if it ever gets to a point where those sections are being abused (like the chat room was ), I would understand if they were no longer part of the forum. There are plenty of places (and one GIANT place, eBay) to sell and buy to your heart's content on the internet, and the MCM Forum just happens to not be one of those places.