All this talk of Git-sympathetic code review tools and nobody has mentioned Gerrit, which seems at least somewhat close to what is being described. Each patchset of each review is its own Git ref and is often referenced in the final commit.

Separately, I know many including myself who would love for code review comments to more seamlessly be integrated into the code browsing experience.

People also seem to be conflating review comments associated with lines of code with an opinionated code review tool.

You can keep the banter with the code and the go-no-go decision separate, even external. But post mootems have worked better when someone realized that one of the team repeatedly calls out a class of errors that bite us later and they’re being ignored. You have the ability to prevent this error. Wise up or that person will decide rightfully that we are a bunch of clowns and leave.

Sure, but keeping that history is just a small part of what I said.

The point about code review still stands.

That's the one major point where Fossil probably falls short: Extending a repository's capabilities would add overhead to every single one of them (and, potentially, to each commit's meta data).