As far as I can tell, this is one of the best-hidden pages on the internet.
When submitting extensions to the Joomla Extensions Directory, you are presented with several severe warnings clearly aimed at keeping over-eager coders from drowning the extension review staff with inquiries on the status of their submissions. A conspicuous warning states that "Inquiring before that time will cause your listing to be suspended for 60 days." Yikes.
While abundantly obvious that inquiries are not welcome, there is also no link to the submission guidelines, or common causes for rejection.