When refereeing a paper, stating I am not an author of suggested literature
As a reviewer, I have suggested the authors to cite one of my papers only once or twice. I apologized for doing that in the notes to the editor, and remarked that I couldn't avoid it because it was really central. I wrote nothing in the blind notes to the authors, and I write nothing when I suggest papers from other people.

I do this because of two reasons:


I value anonymity of peer reviewers highly, and I prefer to avoid remarks that reduce it by unnecessarily providing additional bits of information. There are already unavoidable signs such as writing style and English mistakes, and I don't want to add more.
I believe it is the editor's responsibility to make sure that the referees are not citation-shopping. It can't be anyone else's, because they are the only person with all the information necessary to perform a check. So I have to justify my actions to him/her, not to the authors.


If, as an author or as a second reviewer, I noticed a very blatant case of citation shopping, I would consider it appropriate to write to the editor privately to suggest investigating. but this has never happened to me up to now. (Although there have been a couple of borderline cases.)