May be this is well known. But I still see this in my role as editor for scientific papers (as recent as this week) . Many referees write their reviews of scientific papers using the software MS WORD for convenience. They send this back to the editor using a separate covering letter but careful not to reveal their identity or name in the text of the review. This is standard practice to preserve anonymity. The editor often simply forward such apparently anonymous reviews to the author(s) for his/her information. What is not generally known is the fact that MS WORD automatically inserts the name of the owner of the WORD softwarre usually the author of a review document in the property field of the document. This information is accessible by the recipient of the document. Thus, the identity of the referee can be revealed without the original author being aware of it. Try this on the next WORD document you write to convince yourself.

Of course, diligent editor will transcribe the text of the reviews to a new document or simply remove such identifications. But you cannot count on it.

Thus, every referee should be on guard before you sent out a review written via MS WORD.