Your summary is missing the 500lb gorilla, which makes it extraordinarily misleading to anyone following the discussion.
Let's correct and add information to one dubious statement here:
And, one of my own questions: Why do we want/need PE binaries when ELF are extensible [the "E" in ELF] and have widely supported tool chains? Answer: Because MS is pushing it.
No, the answer is: Because Microsoft only signs PE binaries.
And then let's go up to:
why do you bother with the MS keysigning of Linux kernel modules to begin with?
Here is the 500lb gorilla: Because most implementations of secure boot only accept keys signed by Microsoft.
So in order to get a random Linux-based distribution to run on a generic secure boot enabled PC, your choices are either to remove secure boot (which isn't always possible), hope that the firmware maker included your distribution's key (highly unlikely), or have it signed by Microsoft, which means going the PE route.
ELF may be superior to PE, but that doesn't make it a solution to the problem that RedHat raised. X.509 keys may be an international standard, but they have nothing whatsoever to do with this.
It was a legitimate issue to raise, and it was handled badly by Torvalds and others. A legitimate response would have been "The inability of our kernel to be installed on what's likely to be the majority of computers in a few years is a small price to pay for using superior technologies", not "RedHat just wants to give Microsoft blow jobs", which is immature, pathetic, and doesn't answer anything.