Is it incorrect to use the positive/negative construction when the intent is positive/positive? In other words can these two statements be viewed as equivalent:
Mangoes are sweet and so aren't papayas.
Mangoes are sweet and so are papayas.
When I mean so is, I say so isn't. When I mean so are, I say so aren't, etc.
Is this a regional quirk? I regularly speak this way, and I believe my wife is the first to have ever questioned it (I'm 55 years old). I happen to be from Northern NY near the Canadian border.