All I know is a "funny" thing: If I want to know whether something is considered grammatically correct in Spanish or French, all I have to do is look it up in the Académie Française, or the Real Academia Española, decidated specifically to telling you that. They have been around for a long time, and they get to decide. With real language input, of course, but they still get the last word, sometimes to the point where most people don't even know that what they are saying is "wrong".
On the contrary, English has no such normative institution, and never had. The result: total anarchy, LOL! Just people's habits.
I learned at school that you should never say things like:
-"He did it for you and I" (for the reasons
@SevenFeathers gave - "He did it for me", not "he did it for I").
- Me and Mary went to the store (put other people first, and use the subject! It should be "Mary and I went to the store."
- If I would have money, I would buy a car. (NEVER! If I HAD money, I would ....)
But if I speak like that, some people would tell me they can tell English is not my mother tongue, I sound like a foreigner, or posh, etc.
So, sometimes I ditch the norm, and speak like everyone else, even when it hurts, LOL!
