Although easy to add to documents, Finder comments work strangely, and can prove fragile. They can also be used to conceal malicious code by steganography, but there are better options.
steganography
The UK government doesn’t want to ban encryption, but may see it as a cheap way of winning votes from the easily-impressed.
Why has little or nothing been done to ensure the traceability of important documents which could be damaging if leaked?
Some of our everyday applications employ steganography, usually behind our backs, and without our knowledge or consent.
The Eclectic Light Company 