Misutii thought the main character of Notes from the Underground was an unhealthy INFp , so maybe the unhealthiness\darkness makes him difficult to type. Dostoevsky seems to favour INFj characters in his books, generally, which makes sense if it was his type - it wouldn't be very good logic to say that characters must therefore be a INFj though .
Prince Muishkin does indeed come across as a good example of an INFj.