Is it ethical to cite a reviewer's papers even if they are rather irrelevant? We have just received reviews on a paper, and in reading through one of the "borderline" reviews, I recognized that the "voice" of the review sounded like a researcher I associated with at a conference a few years ago. In particular, they use a certain terms in parts of their review customary to this researcher's homeland. I checked the review committee, and this individual is indeed listed. Upon reading further, they suggest some past work which may be useful -- one of which I recognized as this researcher's work (we have some overlap in our fields).

I have not reached out to this researcher, nor have I shared my suspicions with any co-authors. This researcher and I socialized in a group setting a few years back, but have had no subsequent contact besides being in the same circles on some social media.

While the paper this researcher authored is tangentially related, it is not one that I would consider particularly relevant in our discussion. However, being quite certain of this reviewer's identity, it is tempting to "play up" the relevance of that paper in the hopes of swaying the reviewer.

My question: Is this ethical? I do not have any concrete evidence of this reviewer's identity (nor will I ever look for it), but the fact that I feel compelled to respond in a way different than I would otherwise has my alarm bells going off.

Reworded bonus question: If I believe I've discerned the identity of a reviewer, should I report that to the PC?

Note: This question is intended to be about my conduct, not the reviewer's. I do not believe the reviewer has done anything unethical.
Don't speculate about who the reviewer(s) of your manuscript are. Nothing good can come out of having the knowledge. In fact thinking you know who the reviewers are can cause you quite a bit of grief.

Forget about who authored the review and focus on the facts. You think the paper suggested is tangentially related and not really relevant. Therefore you think you shouldn't cite it. As in similar situations, the next most natural thing to do would be to not cite it, giving your reasons. It would take a pretty unscrupulous reviewer to reject your manuscript because it doesn't cite his paper, and even if the reviewer attempts this, he would also have to convince the editor that he's actually rejecting your manuscript for valid reasons. Remember the editor can see who the reviewer is, and will notice if the reviewer is pushing his paper even if the relevance is tangential. Further, remember that the editor can accept a paper even if the reviewer recommends rejection.

Finally, about whether to report this, there's no point. You won't learn anything about it anyway because the editors can neither confirm nor deny the identity of the reviewer.