I note that it also makes no sense to filter excellent scientists who aren't good writers or who take a long time to write (e.g. PhD dissertation test). If you can do the research, someone else should be able to specialize in writing for you.

At the level where students are required to write professionally, you can hire someone else to do the writing for you. For writing, they typically call it 'dictation', and it used to be standard, to the point that you still see "this dissertation was typed by the author" in dissertations without dictation. For writing correctly, they call it "editing" and many an advisor has had more influence over the actual wording and structure of the dissertation than the person who gets a PhD because of it.

This can be done to about the degree that it's done in the actual professional life of a scientist: someone else can type your papers and grant proposals and make your presentations for you, and no one will know unless they read the acknowledgements. Typically that's not done, or only done on a small scale, because for most people it takes as long to tell someone else how to write it as to write it yourself. When it is done- like when a friend of mine dictated his thesis and then edited it- no one cares, because they understand that it's more efficient that way.

It also seems to me like it makes sense, since so much of science is communicating your results (and using the results of others). If a Gauss does great work, but leaves it in a desk drawer, what's the point? Why would the establishment want to promote that rather than sharing, especially since individuals are so terrible at accurately judging their creative output without external feedback?

Fair enough on the medical school thing, but is this really a serious barrier in something like physics? How hard is it for a talented researcher to learn to write a technical, scholarly document in a timely fashion? Do you know of any good, hard working scientific talents denied access to resources because of their writing ability? Because I know lots and lots of mediocre researchers who are nevertheless perfectly adequate scholarly authors. It doesn't seem like a demanding filter. In my experience most journal articles are terribly written (much worse than your sequences, for example), so the standards can't be that high.

Yes. People achieve better results if they cooperate, but they are judged by what they do if they are not allowed to cooperate.

This system has an advantage of safety -- you can replace anyone in your organization and it keeps working, because everyone has some level of all the necessary skills. (You will never get stuck with the illiterate researcher and nobody to help them write.) So maybe I just underestimate the value of the safety. But maybe the system underestimates the opportunity costs.

Disagree about the med school part. Doctors are always running into strange and urgent situations, having to come up with some tentative diagnosis and fix that's more determined by what's available than by taught best practice. Or at least often enough that they can blog about it a lot. Intelligence and training in a wide array of situations is necessary. Learning all about chemical mechanisms you'll never influence at such a low level, not so much. The first years are also probably too general so switching to nursing is easier.