>I've also found that for email fields you need to be careful to normalize the input (trim, casing) as safari had a habit of autocorrecting the first character to be a capital
Why is that relevant? The standard technically allows for case sensitivity but nobody does it
It can be problematic when you go to look up the account by email address during login and it isn't found due to inconsistent casing.
It's technically true that the part before the domain can be case sensitive, but as nobody does this the gain in UX from people not having to know the exact casing used during sign-up is worth it to me.
Why is that relevant? The standard technically allows for case sensitivity but nobody does it