We're expecting to get $chr(55357), first surrogate, to be replaced by the first replacement of 'a', and $chr(56607), second surrogate, to be replaced by the second replacement of 'a', having them both returned from $regsubex, they would form the code point when being rendered with /echo, just like with $replace.
Not sure how $replace works but it looks like that when $regsubex adds to the final string to be returned when substituing, it checks for surrogate, something $replace isn't doing (and I'm assuming most others functions will behave like $replace).
Which one is correct? are they both correct?
