Cool quadrant, I'll remember it! Thanks!

I’ve never met this in the Russian math Olympiad tradition, would be glad to give you something similar, but I don’t believe it exists… Журнал «Квантик» could be of interest if you by chance know Russian 

Very cool post, even if a bit lengthy! I’d suggest adding a small “Level 0”: sleeping well, staying physically healthy, and getting at least some support from other people. These basics often dissolve a surprising number of problems before anything deeper is needed.  

I’d also emphasize that Levels 2–4 blend together quite a lot. If I’m understanding correctly, Level 2 resembles working with protectors in IFS, while Level 3 is closer to working with exiles. But in practice the boundaries blur: treating protectors with care often brings you into contact with exiles, which in turn requires the skill of “just being with” and to noticing Buddhist hindrances - something very similar to Levels 3 and 4, Healing exiles tends to clarify awareness, without which insight, steadier samadhi, and more authentic brahmavihāra practice are impossible. Those practices, in turn, necessarily involve meeting whatever emotions arise and transforming them in the process. So it’s not only that the levels reinforce one another; in some respects they’re almost facets of the same process.  

I suppose it’s obvious I belong to the “emotional work” fan club 😁

It’s different: sometimes it’s spacious calmness of being able to sit in silence together; sometimes warm feelings of seeing and being seen, when discussing something private with a good friend; or just listening to a really good story. IIRC I also included dates into conversations back then, they have a different dynamic, where a lot of pleasure is feeling a young beautiful woman being with me. 

— this is a very particular feeling you have and those differ a lot in where they appear for different people, how they feel and what they’re about. Not having seen other people’s answers I‘d bet your hypothesis to be wrong. 

I don’t think happiness is a real catch-22. A catch-22 is a structural deadlock; here it’s more a matter of skill. People often get less happy when they pursue happiness because they use counterproductive methods — constant self-checking, chasing novelty, or looking only to external fixes, instead of, say, finding a therapist or working out what’s actually making them unhappy. Theravāda Buddhism frames this well: Right Effort uses wholesome desire (chanda) early on to let go of attachments and build skill, and only later releases even that desire. Likewise, early pursuit of happiness can work if guided by good methods and awareness of failure modes — and rationality also shouldn’t backfire if you read about those failure modes and know why you’re doing it.

Rare to see something heartwarming on LW, thanks!

As said by @Mateusz Bagiński , normal smalltalk is +epsilon, but some more comparisons:
a short smile with a stranger or acquaintance is like eating a very tasty fruit.
90% percentile conversations are all with good friends and leave me high for a few hours. As good as a very good date. No non-social activities come close. 
I don’t actually remember any best particular ones, but the best ones i can recall aren’t about conversations anymore but about presence, which isn’t conversation anymore, I think. They feel extremely nourishing and meaningful and my only comparison is a really, really good IFS or therapy session. 

I'm pretty sure I wouldn't escalate those signs above a rather low threshold given any observers, and my intuition tells me other people would be similar in this regard. So not observing flirting could just imply people don't flirt if you're in the conversation with them. As an extreme example, I've never seen anyone having sex, but it seems as if people do that all the time.

Lately I’ve been trying to use Bayes’ Theorem in daily life — quick guesses, like someone’s nationality from a glance.

What I’ve noticed: my intuition does better when I don’t adjust for general priors.  Corrections like “most people in Germany aren’t Russian” when someone looks vaguely Slavic often pull me further from the truth.

After five minutes of reflection, my best guess: explicit Bayes only really helps out-of-distribution, when we lack feedback loops — new domains, big decisions, reasoning about AI. That’s when 5 minutes of googling or reading a paper can give you better intuition than your System 1.

Is this roughly in line with the Sequences?

https://realityisdharma.com/wp-content/uploads/2018/09/focusing-eugene-t-gendlin.pdf
2nd part of the book
Or get a therapist if it's bad enough.