I've never met a male INFJ, or at least if I have, I didn't recognize him as one. So this is speaking hypothetically.
i think it could work out very well, outsiders could say that it is a boring relationship, but the 2 people involved would never really get bored, since INXJ's in general rarely get bored(from what i know of)
Well, this is probably true. I almost never get bored and it always surprises me when people mention being bored, because it's something I just can't empathize with.
the Wall could be overridden by the fact that each INFJ will quickly sense a trustworthy person in each other, and they will let their guard down quite quickly
Does being an INFJ necessarily mean that you are trustworthy? But I do think a sense of understanding and being understood by the other would likely arise very soon, and that this would hasten the process of the two becoming comfortable with eachother.
conversations could be a bit tricky at first, but that depends more on each one's ability to carry an interesting conversation
Perhaps they'd be tricky at first, but I bet that they could become awesome rather quickly. So much similarity of outlook, and ability to grasp the other's feelings and point of view.
Still I'm not so sure. All of this sounds like it could make for a very fulfilling friendship, but I wonder if romance would actually happen. Would each person feel that the other actually needed them in any real way, or that they completed eachother? What about that sense of fascination that comes from innate differences? My perspective on relationships is that a person is basically looking for their missing half, not their double.
But hey, it all depends on what the people involved find fulfilling and attractive. I'm sure marriages between people of the same type are carried on successfully all the time. There are many other factors that influence two people coming together besides MBTI. Similar life goals, and religious and philosophical beliefs are doubtless much more important.