@jwz @fraying you can simply disable the local comments system and you have an easy to understand, only fully federated comment system for your blog! No context breaks, no mix of federated and local comments, …
The problem only comes with the mix and because WordPress has such a history of local comments I do not want to force users to deactivate them.
To your point share everything, hash usernames: I think THAT is problematic because users do not expect THESE comments to be federated!