You are exactly correct!! My qoute was "when their PM box is full". You wrote "if there is one open conversation slot", if there is one open conversation slot the PM box is not full???
If the PM box is full the seller wouldn't be able to post anything for sale/trade without having to clear their (full) box. If there is one conversation slot open then the seller would get the "one" PM (and get a message telling him/her) but then he/she wouldn't be able to respond because the PM box which would full force him/her to clear their box if they want to continue any conversations??
