I think if someone has mistyped himself, then it is likely that many of his other typings are wrong as well. With misunderstandings about Myers-Briggs vs Socionics, and the proliferation of stereotyped, shallow type descriptions, and the difficulty of understanding the nuances of Socionics theory, it's no wonder there are mistypings.
I take many self-typings with a grain of salt, and rightly so, I think. So many people retype themselves as their self-awareness grows. I mostly try to understand myself through my interactions with others. I form my private impressions of other peoples' types, taking their self-typings into consideration.