The only way to stop buy/sell spamming is to ignore

Besides, having "one" thread for buying/selling, regardless of where it is located, would be a nightmare.

The trading forum works. Plain and simple. Just like CS works. For common items, CS is the way to go. If you have something unique or are trying to sell things as a set, a topic in the Trader's Market can work wonders. Supplement that with the occassional message in CS while doing other CS work, and you're golden.

I personally don't see the point of ppl B/S spamming in CS since the roster of people in any given Balefort Castle instance isn't going to change much. It's better to do your one message, wait (or do CS work), move to another Balefort Castle instance and try another instance. To me, it's better to just stick to CS. Sure you might not make as much with the added listing fees. But the time spent trying to spam and find a buyer/seller is time that can be spent doing other stuff that earns gold and covers your fees.