I use "ain't" all the time in non-formal discourse, and I really don't care if it's considered "bad" grammar or not. The word fits the circumstances, especially when snark is employed.I don't know much about other languages, but the English language has been changing and morphing for centuries. For instance, "ain't": it was originally years ago a contraction of "am I not" and wasn't considered "bad" grammar Now it is.
