If you admit you do not know this, then why say it? I've had opportunities to review papers from people I have co-authored with before and declined the opportu

If you admit you do not know this, then why say it? I've had opportunities to review papers from people I have co-authored with before and declined the opportunity. I've reviewed a paper, then got an invitation from another journal to review the same paper. I declined, but sent the editor my former review. I thing there are strong social mores in the scientific community.