If it's objectively bad code, it should be easy enough to point out specifics.
After pointing out 2-3 things, you can just say that the quality seems too low and to come back once it meets standards. Which can include PR size for good measure.
If the author can't explain what the code does, make an explicit standard that PR authors must be able to explain their code.
After pointing out 2-3 things, you can just say that the quality seems too low and to come back once it meets standards. Which can include PR size for good measure.
If the author can't explain what the code does, make an explicit standard that PR authors must be able to explain their code.