[chris_armstrong]

I would say Australian English relies on this negation even more than British English, to the point of being confusing without more cultural context.

[decimalenough]

Yeah nah... nah yeah, you're right.

[elyobo]

Yeah, Kiwi English also, e.g. describing something as "not bad" rather than "good" is normal.

> How's things? > Not bad.