Alright, you wanted an explanation, here we go. ^^
It does NOT have excessive sub-comms, but what it DOES have is three games in one. Say there are five people in the supernatural, 9 in the city, and 6 in the original (which is being written out, we're going with science-fiction, living on a space station that may be in the gravitational pull of a passing planet).
If they post, they place the game they are in in the subject line, therefore they have the freedom of seeing what is posted where, who to reply to, and who is out there to write with as well. It gives the writer the freedom to choose in one place. That way they are not tied down to one, they can choose. There is one IC community and one OOC community as well as a storyline community. That way, they post for their game, again, they put it in the subject, if they want to look for it, they can click on their tag.