Updates to Classified Ads need to be a new post to that thread.
The intent behind locking the thread is based primarily on the Classified themselves. We want the Ads to be reference material for people, and not modified/deleted after an item has sold or has been pulled from sale. Keeping the threads intact helps set prices/expectations for other For Sale items, as well as setting realistic expectations for potential Buyers.
SMB-less as of 02/04/2012. Our savings account is richer, but our adventures are poorer.