I think the reason that English speakers swap ie/ei is that the pronunciations of these is not really consistent in English (at least in the American accent I speak), and I can't think of any words where both orderings exist but have different meanings. So the general impression I have about this is that I know there are supposed to be rules about it, but it seems pretty arbitrary and unimportant semantically.
Right, we truly don't have a strong rule about differentiating these in the standard American dialect! Most people say STINE for this one, but if you say STEEN, nobody is gonna be confused or tell you that it's wrong.
