a PhD applicant could ask their prospective supervisor’s current grad students what it’s like to work with the supervisor. Yet, at least when I was applying to grad school, this was not very common. 

I often advise doing this, albeit slightly differently - talk to their recently graduated former PhD students, who have a better perspective on what the process led to and how valuable it was in retrospect. I think similar advice plausibly applies in corresponding cases - talk to people who used to work somewhere, instead of current employees.

if the value of welfare scales something-like-linearly

I think this is a critically underappreciated crux! Even accepting the other parts, it's far from obvious that the intuitive approach of scaling value linearly in the near-term and locally is indefinitely correct far out-of-distribution; simulating the same wonderful experience a billion times certainly isn't a billion times greater than simulating it once..

You can't know with certainty, but any decision you make is based on some implicit guesses. This seems to be pretending that the uncertainty precludes doing introspection or analysis - as if making bets, as you put it, must be done blindly.

Strongly both agree and disagree - it's incredibly valuable to have saving, it should definitely be prioritized, and despite being smart, it's not a donation!

So if you choose to save instead of fulfilling your full pledge, I think that's a reasonable decision, though I'd certainly endorse trying to find other places to save money instead. But given that, don't claim it's charitable, say you're making a compromise. (Moral imperfection is normal and acceptable, if not inevitable. Trying to justify such compromises as actually fully morally justified, in my view, is neither OK, nor is it ever necessary.)

Yeah, now that I'm doing payroll donations I have not been recording the data. I guess it would be good to fill in the data, for EDIT: GWWC's records?

The way I managed this in the past was having a separate bank account for charity, and splitting my income when I was paid, then making donation decisions later - often at year end, or when there was a counterfactual match, etc.

Yes!

Understood, and reasonable. The problem is that I'm uncomfortable with "the most good" as the goal anyways, as I explained a few years ago; https://forum.effectivealtruism.org/posts/f9NpDx65zY6Qk9ofe/doing-good-best-isn-t-the-ea-ideal

So moving from 'doing good better' to 'do the most good' seems explicitly worse on dimensions I care about, even if it performs better on approval.

I would be careful with this - it might be an improvement, but are we sure that optimizing short-term messaging success is the right way to promote the ideas as being important long-term conceptual changes to how people approach life and charity?

Lots of other factors matter, and optimizing one dimension, especially using short term approval, implicitly minimizes other important dimensions of the message. Also, as a partial contrast to this point, see "You get about five words."

Strongly agree based on my experiences talking to political operatives, in case additional correlated small n anecdata is helpful.