Posing a question that may have been answered in some of the source material somewhere, but may just have ended up as a blind spot... how does one handle directions in Sigil? 'North', 'south' et cetera don't have much meaning in a city where no sun rises, after all, and suggestions to 'turn left' or follow landmarks only get you so far.
I've got a couple of ways in which native Sigilians might try to orient themselves, but I'll wait and see if anything's gotten presented before then.
In our own game - we use Spireward, Anti-Spireward, and then phrases like "towards the Lady's Ward," or "towards the Hive" - where it is presumed that the shortest of the two routes there is the one being indicated.