As you can see, Nafti was now able to mark the topic sold,he can close it or edit it as well.
I encourage leaving a record but it's up to each member to decide.
Also if you click Nafti's "All Market Listings by: Nafty" link at the top of every Market Listing you can see all his listings with the sold ones clearly marked.
Namepost & MarketPages are getting more advancements every week.