You might already know, that Safari has a nasty autofill bug where it fills email, username and password fields no matter if you set autocomplete=\"off\" or not
This question has already been successfully answered, but as of today's date, the solution didn't work for me without making some oddly particular changes - so I'm noting it here as much for my own reference if I decide to come back to it as for everyone else's.
The only solution I found was to clip the visibility of the fake elements with overflow: hidden.
For the record, the particular case this hack came in useful for was one where an admin is editing the profile of other users and Safari was replacing the email of the user with the email of the admin. We've decided that for the small (but frustrating) amount of support requests that this Safari 'feature' creates, it's not worth maintaining a hack that seems to need to evolve as Safari tightens up on it, and instead provide support to those users on how to turn off autofill.