> I think it's optimized for discussions before integration, which is largely what PR descriptions and comments are largely used for now.

As a GitHub co-founder, whose fault is that? I have seen many great PR descriptions on GitHub that never make their way into the final inclusion in the main/master git history.

Meanwhile the git project links every commit to the message id whence the original patch (for many years now—not the whole history). Which will be available as long as the email archives are out there somewhere.

And the commit messages get reviewed into a good shape. Something that I’ve never seen anyone do on GitHub.