Point 1 & 2: KF was chased out of the US, two US T1 transit providers refused service, Cloudflare along with a handful of American hosters have refused service and social media have all deplatformed Kiwifarms. A special case being made for KF is not an unlikely scenario if enough trannies spam their help/abuse emails (or trannies work at Let's Encrypt). You also admitted that the parent organisation of Let's Encrypt, ISRG, has revoked certificates in the past and you're assuming that they will never do it again. I think they could make an exception, especially for an evil nazi forum with over 9001 confirmed tranny suicides.
Point 3: I mistakenly assumed that the private key was used by CAs for key signing, but it is in fact the public key. Forgive me for that, that was really wrong. The issue does still stand however if you download your private and public keys from your CA, since they generated it for you, they can just save it. I have noticed free SSL (ZeroSSL, Cloudflare) certificate providers doing this, hence why I said that. However it is true that if you generate your own private key, then derive and sign your public key, your CA can't use their private key to decrypt your traffic.
Point 4: Perfect forward secrecy can be achieved in cipher suites where there is a DH key exchange, so TLS 1.3 which KF supports is fine. This is only an issue for weak cipher suites in TLS 1.2 (which
should be disabled) - so for people with old devices or web browsers.
Points 5 & 6: I agree, although false trust hierarchies have been issued in
the past.
Point 7: This is not technically true since if your domain has a CAA record that forces a certain authority to be used, the feds can't just issue a fake cert using any key. They would need to issue another one from the CAA defined in your DNS, which even if they successfully did would most likely be noticed (or not issued in the first place), revoked and rendered useless as OCSP cert validity being checked.
Point 8: HTTP key pinning is deprecated and removed in all modern browsers.