One that I think is super important (and I think used to be on CEA's list?) is transparency:
* The movement was founded on Givewell/GWWC doing reviews of and ultimately promoting charities for which transparency is a prerequisite.
* Givewell themselves have been a model of transparency in their reasoning, value assumptions, etc
* It seems importantly hypocritical as a movement to demand it of evaluees but not practice it at a meta level
* Much of the sea of criticism (including my own) that followed FTXgate involved concerns about lack of transparency
* If as Zachary says the community  is 'CEA’s team, not its customers', it's hard for us to make useful decisions about how to participate without knowing the rationale or context for their key decisions
 

Out of the four "core" ideas, the one I take most issue with is the "scout mindset":

Scout mindset: We believe that we can better help others if we’re working together to think clearly and orient towards finding the truth, rather than trying to defend our own ideas. Humans naturally aren’t great at this (aside from wanting to defend our own ideas, we have a host of other biases), but since we want to really understand the world, we aim to seek the truth and try to become clearer thinkers.

I don't think this "scout vs soldier" is the most important thing when it comes to establishing truth. For example, a criminal trial is as "soldier" as you can get, but I would argue that trials still are truth seeking endeavors that often work quite well. 

Also, merely having a scout mindset is not enough: you could intend to find the truth, but be using really shit methods to do so. 

Instead, I would talk about a more general case of honesty, evidence-based reasoning, and testing/interrogation  of ideas, akin to scientific work. 

Principles are great!  I call them "stone-tips".  My latest one is:

Look out for wumps and woozles!

It's one of my favorite. ^^  It basically very-sorta translates to bikeshedding (idionym: "margin-fuzzing"), procrastination paradox (idionym: "marginal-choice trap" + attention selection history + LDT), and information cascades / short-circuits / double-counting of evidence…  but a lot gets lost in translation.  Especially the cuteness.

The stone-tip closest to my heart, however, is:

I wanna help others, but like a lot for real!

I think EA is basically sorta that… but a lot gets confusing in implementation.

To me, the core EA principles that I refer to when talking about the community and its ideas (and the terms I use for them) are:

1. Cosmopolitanism: The same thing that CEA means by "impartiality." Beings that I have no connection to are no less ethically important than my friends, family, or countrymen. 
2. Evidence orientation: I think this is basically what CEA calls "Scout mindset."
3. Attention to costs and cost-effectiveness:  The same thing that CEA calls "Recognition of tradeoffs"
4. Commensurability of different outcomes: GiveWell, Open Philanthropy, and others make explicit judgments of how many income doublings for a family (for example) are equivalent to one under-5 life saved, or similar. This enables you to do "cause prioritization" - without it, you get into an "apples to oranges" problem in a lot of resource allocation questions. 

I like CEA's explicit highlighting of "Scope sensitivity" - I will embrace that in future conversations. But I'm writing this post to highlight outcome commensurability too. I think it is the one principle that most differentiates EA-aligned international development practitioners from other international development practitioners who have a firm grounding in economics. 

The core of EA is to provide tools for optimizing the marginal impact of altruistic individual efforts given a large array of preferences and beliefs.

The most natural application is selecting optimal recipients of donations for any possible worldview.