I define manipulation
in the bad sense (meaning: literally affecting something is literal "manipulation," but not the kind that Fe gets flack for) as "acting in a way that is not true to how you actually feel, with a purpose behind acting this way in mind." My definition is intertwined with the definition of fakeness ("acting in a way that is not true to how you actually feel").
In this definition, yes, Fe is notorious for being fake
often. But the issue is the amount an Fe-er acts fake comes down to personal maturity, I think. Fe cares a lot about connecting and fitting in, and immature people can be so desperate to fit in so as to not care about subjugating the real person they are in the name of being accepted socially. I don't know any nor could imagine a person regarded as "mature" caring so little about themselves and their personal integrity, and being so desperate for acceptance on a social level, which is why I say I think it's an issue of maturity.
Additionally, Fe can be manipulative as well. Having a goal in mind is not a crime, but Fe, as opposed to like Te, has a compulsion to work in a deceitful (ta da - fake), underhanded, sly, way. The tendency to behave this way probably is logical, as sometimes people will reject suggestions if you tell them what to do but end up accepting your idea in the end if you trick them into thinking it was their own idea or however that's said to go (stated before in this thread, to boot)... but this is still manipulation in my book - "the deliberate action of being fake to achieve an end." This comes down to maturity too, though, for almost the same reason above: I just see this far less often and can't imagine this being a common trait in one who is regarded as "mature" - so, issue of maturity of the person.
I've only read up to page 5 1/2, so this post may be redundant.