This is a bit tricky situation to handle. On one hand, we have to deal with those who wish to sell here, and on the other hand, our admins are not very happy about it, because, they are totally responsible for what's going on here.
This topic is bound to happen in any type of related forums.
Since this site primarily caters to helping out people having troubles with classic systems, discussions about old hardwares, troubleshooting classic systems, helping run (legitimate) games on old systems and via dosbox and so on, I think we ought to keep our focus that way.
And this forum is free from ads and have generally a clean look and feel to it. And our admins are maintaining that way.
I suggest putting a link in the signature to forward to a page like notes at google or yahoo, on which the items being sold can be listed. Those who are interested can contact the seller via a private message (pm).
On the other hand, if the admins are willing, they can open up the long dormant "Arcade" sub section and change the topic to "Trading" section.
Just a suggestion.
Personally, I prefer the "link in the signature" option. It will be cleaner, and we can still buy and sell without problems, and will not troiuble the administrators.
This is a wonderful site. Let's maintain it that way. 😀