If something comes in fashion and everyone's doing it, I_just_can't go along and do the same thing. It feels like it would be like wearing a "Hi, I'm an idiot, how are you?" -sign in my forehead. But later I might go with it, if I decide I like it. I like those who do their own thing.
When I see a grown up man in new haircut, I curse them to lowest hell Im sorry...
My ISFP housemate seems to mimic people more than the average person. I agree that everyone learns to some degree by observation and self-implementation but she does this to a higher than average extent. I noticed some similarities to the behaviours mentioned already in this post. It's particularly noticeable in the use of phrases, tone of voice and style, style of dress, and also in daily routines such as exercise type and time of day, food choices and study habits.
As an INFP I find it uncomfortable especially as the 'observation' behavior is normally quite obvious to me.
I've seen that ISFPs often crave hearing validation that they are 'good' and I'm not sure, but perhaps intense mirroring in some ways is an attempt to attain this praise.