Many times people will assume my statements are directed at them in a personal way when nothing could be further from my mind.
I get that a lot online.
To answer the original question:
In offline life people around me aren't really interested in MBTI so I can't really say they misunderstand my type, but here is what people most often think and usually have no problem telling so either:
I am depressed when I am just feeling tired and withdrawn.
That I am *weak* and can be pushed around just because I am polite and quiet.
That I am sort of stupid because they can't understand my way of relating things.
That I am stupid because I am quiet. I am not stupid on those issues, I am just bored with what most people around me want to talk about!

If I have nothing to say, I am not going to just start blabbing just to fill the empty space.
That I am a space cadet with no grasp of reality, just because I don't use the phrase
"that's just the way things are and always have been" to rationalize the way things are in the world. I know what reality is, I just don't see why I have to accept that is the only way things could ever be.
That I am arrogant, aloof, cold.
That I am uninterested in what they are saying just because I am not quivering and squealing with excitement. If I am nodding and encouraging you to go on then I am interested. *sigh*
Here is an example of something that has happened often in my life in various settings. There is some misunderstanding going on but I am not clear on exactly what it is. Years ago, sitting in math, I am just sitting there listening, thinking and taking notes. (Math isn't my strong point!)
The professor stops and says
"Heart, am I boring you?" His eyes are very angry and the anger vibes are just raditating off him.
Me:
"No." Embarassed and wanting to disappear!
Professor:
"Well, you looked like I was boring you." Voice heavy with indignation.
"May I continue then? If that is okay with you?"
Me:
"Yes." Wondering WTF the dude's problem is and not really knowing what he wants to hear to make him happy.
Professor:
"Oh, well thank you then." Voice heavy with sarcasm.
Things like this leave me bewildered. I hate when it happens and cannot figure out where in the world the person gets the idea I am not listening or whatever and wants to single me out for some weird humilation. This professor didn't do this to anyone else during the whole semester.
There is a certain kind of man (and a few women, but it is mostly men) who I just set off p*ssed without even trying. I wish I could know what it was because it is sort of scary to me when it happens. The man is usually uber male, deep voice, beard, heavy body type, bear sort of energy coming off of them, considers himself very intelligent, mostly higher education. (If it is a woman, she has a more masculine and all business air to her, sharp, radiates commanding energy)
I don't know what they see or think they see in me, but they sure take affront to it. It is something gut level because at times I have not even spoken to them before they zero in on me. Some of these persons have felt free to rage on me and then it is just me standing there with this red faced nut yelling at me and everyone staring... I never know exactly how to handle that, usually by trying to stay externally cool yet assertive and quivering and shaking like crazy inside.