> Is this person routinely writing code so bad that passes all the automatic tests?

Yes, a linter or a test cannot know if you are writing silly, unnecessary code, or re-implementing functionality that already exists elsewhere, or making multiple changes downstream when you could make it once upstream. Only a human can see those things, which is why we have code reviews. And for posterity, yes we are using CI, pre-commit linters, unit tests, integration tests, end-to-end tests, and have formal branching, merging, review process, and coding standards. There are no cowboys here, and nothing that you are suggesting will prevent someone from writing low quality code that requires an excessive amount of time to protect the codebase from.