Shit, until now I assumed chuffed meant miffed or annoyed.

Same this feels like I'm being gas lit here I dont understand how this is real lol

Well, it can be used as both. From memory, it originated in Northern England in military circles, and meant that something was shite and you weren't happy about it.

But, as language often does, it shifted until it's become opposite.

Last I looked it up, it was used predominantly positive, but still had lingering usage as a negative.

However, there's also a more niche usage where it just means one is having a strong reaction of any kind. Often as "not chuffed" as in not being moved by a given thing at all.

Not chuffed means not happy.

usually

But there are still people, in England, that use it the opposite, which was the gist of the comment.