Password hashing is different in 2.2+
FYI, we updated our password hashing in 2.2 to be more secure / standard depending on what libraries are available on your server. Therefore, it's entirely possible the passwords in a 2.2 / master branch install of Vanilla may not be compatible with a 2.1 install - i.e. they would all need to be reset in a downgrade. Just a word of warning / info to the community since I just saw it come up in a support request for someone exiting cloud hosting.