You are only allowed to have one active sales thread open at a time in currency exchange. If you see more then active sales thread that a person has then you should report it and the duplicate thread should eventually get either locked or moved to the trashcan. It sometimes takes a while for a moderator with authority of the poster to work the report though.
I just reported one as being a duplicate (it was a newbie who created the threads) and the thread I reported was quickly moved to the trashcan)
I know it's not allowed, but still many people making multi thread.
And I mostly time report like more then 1 thread in currency exchange + add other thread link too.