Nobody is allowed to reply to an EE thread; you can only reply to threads you have started once a week to bump your add back to the top of the list. Apparently you were allowed to reply to EE adds once upon a time, but people started whining about prices being to high and the thread went nowhere. The threads stay nice and clean now that you are not allowed to reply; if you want to contact the buyer/seller you must send them a Private Message.
Welcome by the way!