And So Don’t I!
One recent item was the use of “and so don’t I” as a positive response to a positive statement (or as a tag). My student’s informant was a Scranton, PA, native, and another student (from Central NY) said it’s native to him, as well.
I certainly heard this growing up in New England, although as a transplant (several generations short of being a native by New England reckoning) I don’t think I ever uttered it myself. I never adopted the non-rhotic accent, either.