INFJ, therefore I must be IEI?

[Absurd]

An MBTI practictioner (there are official ones who have to sit some sort of exam) will look at personal characteristics when assessing your type. If you are talking about MBTI online test only then i'm curious what you see is the difference between preferences and personal characteristics, assuming that the preferences don't change...or do they?

MBTI is based upon Carl Jung's notions of psychological types and it was first developed by Isabel Briggs Myers and her mother, Katharine Cook Briggs. Isabel’s husband, Clarence Myers, was a lawyer and because Clarence was so different from the rest of the family, Katherine became interested in types. She introduced Isabel to Jung’s book, Psychological Types and thus they both became avid type watchers.

And what I was trying to say when I wrote preferences is the extraversion/introversion, sensate/intuitive, thinking/feeling, and judging/perceiving axis. Preferences in short , not personal characteristics which can be interpreted in many ways.

As for taking an online MBTI test and scoring some four-letter type? Well, sorry I do this again but you might want to ask people on here, make a survey inquiring whether their MBTI type changed after some time or not...

I'm sure you will stumble upon interesting replies (same with Socionics).

You can think of it in terms of that Park thread as well - the stuff you picked (not picked) are preferences, not personal characteristics. Preferences allow for a choice, personal characteristics, don't.