Double posting has been an issue lately. It is the same as 'bumping' a thread, and will be dealt with as if you are bumping. Actions include issuing an infraction, and even temporary banning. The posts will either be merged or deleted.
The marketplace also has a rule of one (1) thread per category every five (5) days. Make sure this is followed or the threads will be deleted (and infractions may be assessed).
Regards,
Nick