I've been following the stats closely. There were actually several times that the active users ticked down and then ticked up the next day, the most recent being September 19/20. But I suspect that may be a statistical artifact, whereas the increase on September 28 is legit. It looks like about 1000 new accounts were created/became active on that day.
User attrition has slowed significantly in September compared to August. We should stabilize somewhere in 30,000 range for MAUs before the end of the year, which is not too shabby. We are unlikely to see another big wave of growth until the code is significantly more mature, but the current userbase is fairly well established and self sufficient.
I can't wait until we get that next wave so we can have more sports fans and humanities types, but you guys are alright for now π