The number of users dropping in June when many bot accounts were removed, and then rising again at the same time that >1500 new servers were added, while MAU does not rise at the same rate, seems to suggest that many are in fact likely bots?

However, the MAU is rising, so that indeed is a sign of health even if the precise amount of traffic by humans is unknown.

And bot accounts serve useful purposes too, sometimes posting more worthwhile content than many humans.:-)