I regards to INFJ barriers, yes, they are there but for me the question is where. I have mine, true, but they are set way back from the surface. I am extremely warm, open, approachable...easy to get to know. I have rafts of pleasant, long term friendships based on this. But, I am also legitimately (for better or worse) a deep person and so even if persons know me well, actually understanding me seems to only remain the purview of the few, and that not based on my own barriers, but more based on the curiosity/interest of the other person. If someone and I share that unexplainable link, I am a completely open book.
I say this by way of hypothesis.....INFJs, due to varied life circumstances, experience the same basic type-dynamics over a very wide range of behavior. We are the same, but we aren't.
Anyway, I just hope INFJs don't feel too compelled into a withdrawn, secretive existance, when I believe it is very possible (and quite likely) to be an INFJ and still be quite open, warm, and genuine while retaining that deeper existance that is truly a gift.