I’ve contrasted some of the counts against and old profile database from end of 2018 (curtesy of @Piggy at the time), and one of the main discrepancies in the count until end of 2017 comes from the fact that the official stat for December 2017 is
partial, displaying 63.756 users, whilst the real count is 191.454 (which is consistent with the end of 2017 boom). If fact, if we drill down on the forum stat page for December 2017, we’ll see it only runs down until the 13/12/2017 (which is also a partial reading). That account for most of the data discrepancy between @ImThour and @hosseinimr93 (there are other minor odd ends).
I wonder how many of those accounts haven’t even made a single post <...>
As to the number of accounts themselves, I haven’t got any recent data, but
in July 2018, 72% of the accounts were brand new, meaning bot created, nuked, or simply created without posts. That fact is important to understand when we discuss the number of created accounts on the forum (active accounts are therefore way less).