What about this story is inspiring people to write smarmy comments and sign them with silly pseudonyms? Bigtable itself doesn't provide a schema or constraints

What about this story is inspiring people to write smarmy comments and sign them with silly pseudonyms? Bigtable itself doesn't provide a schema or constraints, but it provides primitives that would allow you to implement them AFAICS. That's why I mentioned the idea of implementing a MySQL backend that uses BigTable as its storage -- MySQL would contain the schema and constraint logic, BigTable would provide the sequentially-consistent data storage.