Mistakes are possible but language variants with different rules are not "mistakes" no matter why the variation came about. Intentional thought or planning is behind about 0.5% of our standard English. Why hold other dialects to a higher standard?
I'm not. I'm perfectly fine with saying that language A (be it well established or not) is language B with mistakes, even if language B itself came about through mistakes.
I don't mean that everyone who speaks makes mistakes by doing so. I mean that the language came about through mistakes. That, in my view, makes it quite appropriate to say that language A is language B with me stakes.
