Re Fi or Fe being selective. I can see what you are talking about and I think we both do this, but in different areas. Working on articulating this properly in my head because I've noticed both things at work in inverse ways.
An example of doing something you don't feel like for someone else's sake that you care about - Maybe you hate hospitals. You always have. Yet someone you really care about has fallen seriously ill and needs your presence there. I think Fi is more likely to say, "It's not them. I just don't like hospitals. I'm staying home." whereas Fe reasoning might be more like, "I hate hospitals, but so and so has been there for me in the past and they need me right now because there's no one that can fill that place for them. I guess I'll go, even though I really don't want to." Another example might be going to a musical with your SO. You don't really enjoy musicals and you have no real interest in seeing this one. However, your SO has checked around and they have no one else to go with and they've offered to pay for your ticket. They'd really like to have a shared experience and it matters to them. Fi reasoning might go something like, "I have other things I'd rather do with my evening and I don't even like musicals. Is it such a big deal to go alone?" Fe reasoning might be more like, "They did this this and this that I wasn't interested in. I guess I'll go even though I don't really want to and make it fun for them". Fe focusses more on the fairness aspect and also how it will impact on other people. More priority is given to sacrifice for people closer to them, because more investment has been offered in the past which obligates. (I'm not sure about this, because this might only be NFJ Fe, or it might be more individual than that). Fi is much more about the individual and being authentic to their feelings instead of doing things out of obligation????? (I don't really want to presume to say, because I'm not sure what it's about). I'm not even sure if these examples sound fair to Fi users, but that is the kind of thing I'm thinking of.
You were doing so well and now you've gone and made such a rookie mistake in function interpretation. I'm sure you meant well, but you must realise this is an unfair comparison. You've basically compared positive example of Fe behaviour with a negative example of Fi behaviour. I'm not saying that there isn't some truth in it, but the truth is more complex than that. I would describe the Fi example you used as an unhealthy form, that is perhaps more commonly seen in tertiary/inferior usage. To me that's just bad Fi. I'm not saying I've never been guilty of it, but for the most part this is not how I would describe my behaviour on a day-to-day basis (nor would others, I imagine).
I would break it down this way:
Fi - driven by the individual (focus on yourself or the individual experience of another)
Fe - driven by others (focus on behaviour towards others and their behaviour toward you)
These can both be used for positive and negative ends. To compare the extremes of both:
Fi at its best
Deeply empathic. Strongly connected to others. Forgiving. Authentic. Thoughtful. Benevolent. Unbiased. Principled. Selfless. Kind. Generous. Complete understanding and respect for what others think and feel. Enables others to be at their best and acts as advocates for them. Strong sense of obligation to what is right (eg. to be kind, to be there for friends). Helps others by anticipating and fulfilling their needs.
Fi at its worst
Selfish. Apathetic. Self-indulgent. Self-righteous. Tactless. Bears grudges. Total lack of consideration of the impact of own behaviour on others, OR use insight into others hearts/minds as a weapon (eg. cruelty). Willing to justify anything to serve own ends. Morally inconsistent. Expects something for nothing. Refusal to adapt behaviour - "my way or the highway". Insensitive to the feelings of others. Example: someone expecting their SO to go along with their interests/hobbies but refusing to participate in the interest or hobby of their SO (or doing so but complaining constantly about it).
Fe at its best
Compassionate. Inclusive. Fair. Supportive. Self-sacrificing. Considerate. Principled. Selfless. Kind. Generous. Create unity and maintain harmony. Inspires and assists others to reach their goals. Strong sense of obligation to others (eg. to help people, to be supportive). Helps others for the pleasure of doing so.
Fe at its worst
Exclusionary. Vindictive. Disingenuous. Us vs. them. Manipulative. Unfairly projects negative intentions on to others. Refuses to accept others think/feel/behave differently. Reciprocity taken to an extreme - always keeping score. Treats kindness/morality as a transaction, or as an investment on which they expect a larger return. Expectation of gratitude from others. Chooses to blame others for everything, while elevating self to sainthood. Example: the 'nice guy' who expects sex/a relationship in return for kindness towards a female acquaintance (ie. "I deserve sex/relationship with you, because I was nice to you") and then is outraged and accusatory when he doesn't get it.
Do you think those are fair descriptions? Correct me if I'm wrong.
In terms of what you're actually trying to get at, I would say that Fi is selective about what it determines are its obligations. Fi decides what is right or wrong and will act in accordance of this - and if this is done badly, it can be, "I think I shouldn't have to do what I don't want to". But if you are using Fi well, you don't choose obligations based on what you want. Instead, an inner part of you forces you to take certain courses of action. Often it doesn't feel like a 'choice' at all; it is an internal obligation to do the right thing. OTOH Fe sees obligations in broader terms and as coming from external sources; the sense of pressure comes from other people to match a perceived standard. I don't feel that pressure from others. I don't feel pulled this way and that by what I think others expect of me or need from me. I'm the one that puts myself under pressure. I crack my own whip, so to speak.