I've never taken the official MBTI exam, but I've taken several different tests online and get about the same in each one. I'm strongly INP, but on the line between T and F, with usually a very slight lean to F. Both INTP and INFP describe me equally well, and I can get annoyed with people I meet who are extremes of either side
I've always been an avid debater plus equal parts daydreamer and deep thinker. I noticed the thinking/feeling differences in people before discovering MBTI and codified my interpretation of those functions for myself before I ever knew I was an INXP
Logic/Objectivity are tools for generating understanding and cooperation in fairness between varying value systems, but when unbalanced by feeling/subjectivity can lose sight of its ultimate purpose and lead to actions and attitudes which betray human need. I've seen this most often in people who cling too stubbornly to blunt objectivity and drive people away because they can't be convinced to turn their logical functions towards developing social tact. They may be presenting what they think is the best objective compromise, but without applying Feeling, they're terrible at selling that compromise to others. Since discovering MBTI, I've especially noticed that introverted thinking types tend to run information through their value systems and present the conclusions as fact, while refusing to admit that those conclusions are in fact the product of a value system. I've seen many discussions turn bitter over this behavior.
Feeling/Subjectivity are used to generate value systems, which are inherently relativistic in nature, and thus (whether admitted or not) serve as a launching point for the logical functions, as all formations of objectivity and logic begin with interpretation of information that is limited by the subjective limitations of knowledge/experience. Feeling is also responsible for the most fundamental fabric of human relationships - that connection (good or bad) which may be explained only after it is developed. I think this is the part of us that gives us direction and meaning in life. Without the value systems generated by feeling, there is no way to generate priorities in life which translate into goals and eventually action. If feeling is left unchecked by thinking, it can also easily betray itself because selective use of objectivity is required to create the harmony it desires. Without any Thinking bridging the gap to value systems held by other individuals, which is what enables fairness and cooperation, pure Feeling is doomed to destroy the connections it creates.
I may be completely missing the point here, as I haven't read much about the stacking of functions in MBTI, but I hope I've offered something. I really think and feel that T/F is a very important balance for people to achieve and respect.