UPDATE: This fix has unraveled, and Barrie England's is 404ing as well.
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This has been fixed for you specifically. We'll be making a check up across the network later to see if there's any stragglers that are broken.
This results from the new authentication system that automatically creates account - we happened to fail to sanitize spaces in one particular field. That happens to be the one that affects the author posts link and happens to not be fixable from the UI itself. Oops.