Intro: People of same MBTI type place slightly different emphasis on their cognitive functions. These differences in functional emphasis produce discernible differences in attitudes and behaviors and gives rise to two subtypes: one defined by its leading function and another by its auxiliary function.
What if I cannot identify with either of the subtypes? Subtypes demarcate two poles of a single continuous spectrum. Some INFJs may find themselves on the far ends of those poles and be able to easily associate with either subtype. Many others may fall in the middle in which case you won't have an easily distinguishable subtype.
Why are there only two subtypes? Because the functions are all connected to each other through three jungian dichotomies: Extroversion-Introversion, Intuition-Sensing, and Thinking-Feeling. Weakening or strengthening one function will produces a domino effect across their entire functional layout. For example, strengthening INFJ's dominant function Ni has the result of weakening sensing, Se, in accordance to Intuition-Sensing dichotomy and Extroversion-Introversion dichotomy, as well as weakening of extroverted ethics in accordance to Extroversion-Introversion dichotomy, since Ni is introverted function. Two subtypes exist since one can either increase effects of the dominant function or the auxiliary one.
What effect does this have on other functions? Strengthening of introverted intuition in intuitive subtype of INFJ has the effect of strengthening introverted logic, Ti, weakening extroverted feeling and sensing and thereby enhancing introversion of the intuitive subtype. Intuitive INFJs thus have heightened introspective and analytical abilities, lowered sensitivity to ethical transgressions, and a vivid imagination, but may seem inert, prone to doubt and excessive mental rumination, and in poor contact and awareness of the reality of everyday life. Strengthening of extroverted ethics leads to bolstering of extroverted sensing as well as de-emphasis on introverted intuition and introverted logic, which makes Fe-INFJs more dynamic, diplomatic, and energetic, less prone to over-analyze things into oblivion, but also more sensitive to criticism and conflict, more "flighty" and inconsistent.
Do subtypes affect MBTI typing? In general, yes. Intuitive INFJs are prone to mistyping themselves (and getting mistyped by others) as introverted logical types such as INTJ and INTP. This is especially true if they happen to be in enneagram competency triad (1,3,5). As its name would imply, this triad prioritizes competency and prefers to solve problems in an objective, unemotional manner (INFJ 1s are particularly data rational and may have more of a scientist bent to them). This gives them the appearance of MBTI's logical types. INFJs far off in the ethical spectrum are highly dynamic and may have trouble keeping consistent and internalizing the logical framework behind the MBTI types and are prone to switching across several different types and mistyping themselves as ISFPs, INFPs, and ISFJs.
Ni-INFJ: The Idealist
The intuitive subtype appears as a quiet, tactful, languid and diffident individual. They seem torn off from reality, inert and poorly adapted to life. However, such impressions are erroneous, for they possess a fine intuition, which aids them in establishing useful connections and obtaining support from influential people. Seem externally serene but sentimentally are disposed to experience moodiness and bouts of melancholy. While their voice at times seems monotonous they often induce a light surprise, even full interest, from the interlocutor. Outwardly are pensive, slightly strained/intense. Prone to emanate sadness masked in sardonic irony. Speech is measured, smooth and intimately heart-felt. On their face they almost constantly exude a polite half-smile that easily wins people’s trust. Gestures are modest, shy. Gait is ponderous, elegant.
Gentle and considerate person. In his heart is a dreamer and a romantic. Has figurative, associative memory, and can recall experiences from the past down to the smallest detail. Reminiscing about the past, he recalls all the mistakes and mishaps, then extracts from them lessons for the future. Thanks to a strong intuition sees short-term prospects of affairs and relations, but because of the tendency to idealize everything may also overestimate them. Under any circumstances, does not lose hope that in future everything will be better than the current situation.
Somewhat unsure in himself, is inclined to doubt and hesitate in cases he has to speak or act decisively. He does not like to rush, can delay carrying out tasks and finding solutions to problems to an indefinite period of time, or even never get to them. Does not aspire to leadership, experiences difficulties with organizational functions. Gravitates more towards intellectual sphere of activity than to direct management and production.
In work, can become distracted by irrelevant, minor things, and thus run out of time to do the more important tasks. He does not like stereotypes, conventionality, strict order, having to follow strict rules and regulations. In his apartment or at his workplace may allow for artistic mess and disorganization. Being economical and having good entrepreneurial judgment is not in his nature, because of this he might miss out on promising opportunities.
Does not like routine and monotony, desires new experiences, gravitates towards interesting and unusual people. Likes conversion about various unconventional and esoteric phenomena. Willingly accepts and promotes imaginative ideas and innovative approaches, but is wary of new ventures, in such cases prefers to yield initiative to strong-willed and assertive people. However, if necessary, exhibits outstanding diplomatic skills, achieving success where others have failed - straightforward and eager partners, don’t place much value on flexibility in relationships.
Sensitive and attentive to people, tries to maintain smooth relations with everyone. Due to the absentmindedness sometimes forgets to fulfill his promises, but then does his best to make amends. At the same time, exhibits tolerance towards other people's flaws and weaknesses. Does not know which of the two disputants he should favor, therefore, will try to reconcile them.
Needs moral, physical, and material support. Respects strong, influential people. Relationships that have been exhausted does not break immediately, as he grows accustomed to people. Knows how to wait patiently and how to adapt to any circumstances. For the sake of good relations with family, tries to meet the demands they put on him, tries to develop practical skills, perform work and fulfill his family responsibilities.
Fe-INFJ: The Diplomat
The ethical subtype makes an impression of a soft, charming and emotional person. Usually look inspired and optimistic. Possess a fine sense of humor allowing them to list their problems and failures while smiling. Are ironic, crafty, unpredictably and inconsistent in behaviour and conversation. Creating original contrasts, they can unexpectedly prick and then just as quickly embrace/kiss. Artistic and charming; are eloquent in dialogue, occasionally portraying shades of familiarity and impudence. They’re generally affable, kind and careful. Easily draw attention and thereby attract people; talent towards persuasion: states requests in such a manner that it is difficult to refuse them. Movements are graceful as is their gait. Speech is emotional, rich with shades, sometimes melodious.
Emotional and charming, easily and naturally comes into contact with strangers, predisposing them to trust with his warmth and sincerity. Able to cheer up others, make them laugh with his unusual antics and utterances. Figuratively, with a good sense of humor, tells stories of what he has experienced and seen. Well versed in the feelings and sentiments of others, knows how to establish useful contacts in order to achieve his goals, how to find the most suitable candidates for the job conceived. Often phrases his requests in such a form that one cannot refuse him.
He loves to be at the center of attention. Elegant, skillful in his ability to please, readily gives compliments to others. Able to find an individual approach to each person. He loves and knows how to reconcile a dispute. Often is ironic and sarcastic, but states even the displeasing things as if in jest, and with a smile. Unobtrusive in his feelings - if he does not see reciprocity, he will distance.
Easy lights up with a new idea, but can quickly lose interest in it, if it requires a lot of patience and effort for its realization. He needs praise and encouragement. Sensitive towards any criticisms, or if his work goes unnoticed by others. In such cases his enthusiasm for work is lowered. At the same time, praise issued in advance will encourage him to overcome difficulties, helps to gain confidence in himself.
Somewhat touchy and suggestible. Has a tendency to show off to others his physical or intellectual suffering. If he senses danger, his uneasy and restless mood will be transmitted to others. In my heart is very vulnerable and very upset by their failures. Internally contradictory, prone to abrupt mood swings from laughter to tears, and vice versa. Proves his case passionately, accepts advice only when he has calmed down, until the next emotional outburst. Needs the support of strong-willed, energetic people.
Readily shares his problems with others, looking for sympathy, understanding, support. Consults with others before making important decisions, though does not always follow their advice. Independent by nature, impulsive, unpredictable in his actions. Prone to impromptu acts and improvisations.
In some situations, evokes awe and admiration in others by exhibiting fearlessness in dangerous situations. Nonchalant and imperturbable, but this is only a tactic that allows him to make an impression on others. This serene state is infectious; it passes onto others, allowing them to distance from their everyday worries and problems.
Graceful in his movements, shows refinement, good manners, dresses tastefully. His residence is clean and neat. He has an aesthetic taste, like ornaments and refined decorations. Appreciates comfort. Cares about his own appearance as well as those of others. Can buy extra stuff, wasteful and uneconomical. Does not like those who are stingy over small sums. Does not place much value on things, his own or those of others. Lending or loaning something, may forget about them for a long time. (source)