If you make a post to sell and someone buys by PM but does not actually post in the ad, can you leave a iTrader for them. .
Yes. You can as long as you made a deal it is fine. It is not necessary to post in thread to exchange itraders
A follow up on what dpsubi said, his info is accurate as long as thread is in buy, sell, trade, excluding freebies.
The answer to that, and any other iTrader question you might have can be found in this thread: iTrader 101 - Part I