People sometimes assume that my best friend is a thinker because she is gifted and a nerd in business school and took sciences for her baccalaureat. She is not an INFJ but an ISFP though, but still, I can see to which stereotypes people respond. She can be very rational and think but she acts more on feelings and admits it herself.
On the other hand, I thought I was a feeler when I was younger and actually acted like the worst stereotype of the irrational INFP sometimes (with obvious thinking outbursts) because it was an ideal to me. I was disappointed when I read "NT" for the first time, I though I was SF.
One my closest friend is hard to tell between INFJ and INTP because she has a strong Ti and Fe but does not seem Ti dominant. Another guess would be ENTP (because she seems to be using Ne sometimes but I do not really get Ni but she can fake strong Se easily so I'd think she got Se as a function) but she is an introvert. I do believe that she is an INFJ with a tendency to fall in Ni-Ti loops sometimes, but this is mostly because she brings the best out of me and is the only person who actually know that I am a sentimental, have feelings and we share them.
She also admitted that she was unsure to whether she was an F or a P (she would say P though, and it is even more likely than me sometimes but I believe more in functions than main dichotomies for this one) because she seems to use both more or less equally. People see her as a T, I see her as a closet F. INFJs often strike me as very close to being thinkers on forum (and almost no thinkers seem feeler but I would assume that they enjoy the stereotype online because we can use feelings - it is either that or I am a repressed feeler and I was right when I was a teenager) and very close to the way I function with a slight interesting difference because I just can see the Ti in your speech sometimes more than the Fe.
I guess it also has something to do with the topic we're discussing, that your Fe would be more obvious in real life and in certain situations while mine would appear clearly inferior. Plus, there is the Ni working differently than Ne.