Why is it that half the time your posts sound like I could have written them? I too have been warning my SO and other friends [at least the online ones - not the real life ones] about my moodiness and need to withdraw every once in a while.
The bolded part ... about Fe-politness is extremely accurate about me as well -- but in a slightly different way. I kinda become a little short but coldly polite as opposed to really polite. I'm typically charming, so when I detach and try to isolate .. the most I can muster is words like "ok" .. "yah ..." and I keep repeating mundane questions to get the other person to continue talking while I'm actually in my own head.
Do you also sometimes start feeling fake and inauthentic when just being polite, while wanting to express exactly how and why you're feeling a certain way? Maybe that's more of a 4w3 thing.
For me it's one of the most difficult binds for me .. The result is actually kinda amusing [now in retrospect anyways] .. it's like in the moment, the feelings are beyond intense and I end up saying/acting in a way that makes another person worried .. yet, I don't actually want them to worry .. yet I do want them to at least show some concern .. and then when I don't get that kind of concern I continue to act in ways that'll get the desired response.
Maybe it's because I'm tertiary Fe as well and therefore kinda manipulative with other people's feeings [really ashamed about that]. So knowing that I manipulate, I try not to manipulate but still end up doing it anyways.
Mmm..I guess that it is the Fe that makes a difference. What I try to do, to not worry the other person in a convo, is focus solely on them and what they are saying, despite it being hard, so I can end the convo swiftly and neatly and excuse myself asap. The reason I do this is because experience has taught me that if I allow my mood to seep through when I havent had time to reflect yet (Fi), I will overload the person without wanting to and Ill feel ridiculous, exposed and ashamed of myself, instead of getting the help I need.
Though I too swing to the 2 dark side occasionally Ill do it by..I dunno how to express this....ehm, by 'appearing' sort of not present instead of saying something. People automatically respond to that with like extra care and asking like 'are you alright?' which i can shrug off, meaning I dont have to have the disastrous convo of doom, while letting them 'feel' Im a bit off today. I try to do this only with people who know me somewhat and who I know actually enjoy my presence and not at more formal events with like acquaintances and strangers only. That way, I often can put in that I actually just need some space and they will be most understanding, while I do feel like they care. I try very hard *not* to do this, but on days where Im melancholic, blue and gloomy and I cannot change that mood, it turns into brooding and others do notice. I actually enjoy that state to a certain degree, and I try telling people not to worry about it and just let me enjoy their company in quiet..which seems to work. It is kinda funny to see how people sort of..feel the need to like check you out coz you are vibing 'off'

(my w5 finds it an intriguing experiment

) Most people do respect your wishes when you vibe off, and you seem like you can handle it (and if there is one thing I can handle, its my moods), so they just let you be in peace, which I very much appreciate

Aside from that, most people seem to find it a curious thing, poking you a little (which can be a nice distraction) and actually enjoying it as entertainment..which helps alleviate my guilt of doing it.
As for feeling fake (I identify with both w3 and w5 btw)..that only happens when I truly am deep in those moodswings, as usually my Fi feels guilty about bothering others with this and I learned a long time ago that people really dont *wanna* know and I should respect their wishes. Its my crap to deal with, not theirs, after all. As I said, the dark side of the 2 isnt unknown to me though I will try to minimise the damage by just reassuring people I will be ok and that I just want to be near them. In my darkest moments, when nobody takes notice, I can get irrationally resentful, but it usually ends up making me smile at the resentment as I realise that it isn't their job nor their fault as Im not speaking up. And that in itself can give me some relief, as it allows me to look ironically at the mood that initiated this whole thing. It does not always break it, but I find a sort of bittersweet enjoyment out of riding it out
As for manipulation..we all need to have our dose of oxytocine and feel like we are cared for, especially in our darker hours, and we all reach out/manipulate other people to get it. I try to minimise the negative impact my reaching out would cause to people, and I try to show myself the compassion I would show someone else in my position. This is a need I have, and I shouldnt chastise myself for trying to fulfil it, as long as I try to do it in a minimally invasive way for the other person and preferably in a way that they too get enjoyment out
