When reviewing code you sometimes miss things. It's not an exact science. You also sometimes get a bad feeling without being able to say exactly what's wrong -

When reviewing code you sometimes miss things. It's not an exact science. You also sometimes get a bad feeling without being able to say exactly what's wrong - it just feels/looks bad. That's when you should seek additional input from your peers. Rejecting code based on 'smells wrong' can be sane. The submitter should then explain better why the code is sane.