This difference between Fi judging a person and Fe judging the emotion is expressed in the type of emotions and feelings involved.
Fi deals with emotions such as hate, love, compassion, sympathy, respect, trust, loyalty, moral outrage, dread, resignation, cynicism, shame etc. All of these involve judgments about other persons, objects or events.
Fe deals with emotions such as fright, startle, surprise, shock, anger, grief, sorrow, anxiety, joy, euphoria and depression, and is less inclined to pass value judgment on another person, although another person can clearly be seen as a positive or negative source of emotions, and as such can lead to a value judgement.
Affective emotions (Fi) last longer than reactive emotions (Fe), which confirms my own observation that Fi value judgements have a much larger long-term effect: If you are the object of an Fi value judgement, this is much more difficult to overcome than being the subject of an Fe value judgement. With the latter, you, the object, is being evaluated as a source of pleasant of unpleasant emotions, which may change when you change your emotional expression. But this is more difficult with Fi, since Fi involves the emotions of the person making the judgement about you, which are much more difficult to change.
With Fe, what you see is typically what you get, as there is not much beating around the bush. Fi, which drives rationalized behavior (in the non-Socionics, sociological sense) much more than Fe, all is not what it seems.
Let me elaborate with an example: suppose you have violated the boundaries of an Fi ego type, how do these react? First of all, it depends on how serious the violation is. You might never know the countermeasures the Fi ego takes against you, because it is done so subtly that you never notice measures are being taken or can't make the connection; or the measures are taken by proxy, meanwhile the Fi-ego behaving with courtesy and respect towards you. Or they are taken after a while, when it's no longer apparent what motivated the measures). It can be something as simple as not being invited for tea, or playing dumb, pretending to not to have the skills required to solve another person's problem. But when the matter is serious enough to be dealt with immediately, the response is quadra-dependent.
As said, with Fe, what you see is typically what you get. If you violate the principles of an Fe-ego (which is more likely than violating their boundaries), they are more likely to retaliate openly. For example, they will try to modify your feelings as to make you feel bad (and thus make you back off or toe the line), either directly or by turning the group emotionally against you.