A particularly rare personality type
An INFJ strength, they can see through dishonesty and disingenuous motives, and step past manipulation and sales tactics and into a more honest discussion
Inspiring and Convincing
Another one of the INFJ's strengths, they have fluid, inspirational writing style that appears to the inner idealist in their audience. They are also great orators, they speak with warmth and passion if they are proud of what they are speaking about.
Determined and Passionate
This is yet another strength. When INFJ's come to believe that something is important, they pursue that goal with conviction and energy that can even catch their friends and loved ones off guard. They will rock the boat if they have to, something not everyone would like to see, but their passion for their chosen cause is an inseparable part of their personality.
This is a weakness of the INFJ's, and in my opinion it is this biggest one. When someone challenges or criticizes their principles or values, they are likely to receive an alarmingly strong response. They are highly vulnerable to criticism and conflict. Questioning an INFJ's motives is one of the quickest ways to their bad side.