Cfrgtkky

So, I have heard of people not censoring when people do so. There have been at least some controversies in some fields where this has happened. See for example, https://www.quantamagazine.org/a-self-aware-fish-raises-doubts-about-a-cognitive-test-20181212/ . For that reason I would strongly recommend removing the signature. Anonymity is important, and I personally (and other people) have had bad experiences with referees who have deliberately unmasked themselves. A big part of the concern where a referee has deliberately unmasked themselves is that if they are prominent in the field there's a possible implied intimidation or threat of retaliation for results they don't like. Also, it is possible that the file you got was intended for the editor and wasn't actually intended to not be unmasked in the first place. But regardless, editors should do all they can to keep the referees anonymous.

There are a few different cases to consider. First of all, there is the question of whether a journal's policy even allows for signed reviews. I think that most journals do not have an official policy about this. However, if there is a strict prohibition against non-anonymous reviews, then the editor should remove the identifying information before sending the report on to the authors (and any other relevant parties, such as other referees who are working on the same paper).

In the more likely event that signed reviews are not outright forbidden, then editor should look at the additional question of whether the referee really intended to make their identity known. From the report alone, it may or may not be clear whether a referee is intentionally choosing to dispense with anonymity. If there is just a signature at the end of the report, the reviewer might have added it out of absentmindedness. If the situation is unclear, the editor should check back with the referee, to see whether they actually intended to include their name before passing that name on.

However, I have seen one review that concluded with:

I choose to sign this review.

[Referee's Name]

In that case, it was quite clear that the reviewer (who was both a very senior person and giving a positive report) was not worried about maintaining anonymity. In a clear-cut situation like this, a referee can simply send the authors the report without any additional concerns.

If the journal policy is to maintain anonymity then it should not be done, even if the referee has indicated her/his name can be revealed. The reason is simple enough: if the review is not signed and one knows that John Smith from Big Name University usually signs his reports, then one can deduce the referee was NOT John Smith, which may help the author conclude about the identity of the real referee.

"Should" or "should not" is impossible to answer in the general case. Some journals may have a formal policy one way, some may have a policy the other, and I suspect that the vast majority have no formal policy about what to do with signed reviews.

There is a (small and localized but real) debate over whether reviewers should sign their reviews, and at least for a while it seemed that there was a small movement toward signed reviews. I can say that I've signed reviews and at least in some instances they have been passed on to the authors, so there are some journals and editors who don't have concerns about this.

As ZeroTheHero touches on, anonymity is not a property of an individual, it's a property of a set of people. You can't have a single anonymous reviewer; if of the set of possible reviewers, all but one sign their name, then whenever there's a review that isn't signed, everyone knows whose it is (note my wording does admit the possibility that there are people that are qualified to review but haven't been asked to do so by the journal, in which there would be some anonymity in that people might be unsure as to whether the review is from one of them, but for many papers the set of people qualified to review is quite small). We don't let voters waive "their" right to secret ballot, because if all the voters for Party A sign their names on their ballots, then we know that any voter whose name we don't see voted for another party. Since anonymity is not a property of a single person, it is not the right of a single person to waive.

Now, if you as a journal want to have limited anonymity, that is your choice, but it's not the reviewer's choice.

I was involved as a referee in a case where the authors turned around and invited me to be a co-author, and I've heard of that happening before. I didn't accept the offer, because the paper wasn't something I wanted my name attached to, but I can imagine cases where it would be appropriate to do so.

I think the editor should delete it to avoid spoiling the puzzle game of figuring out who the reviewer is. (Easy one is when they ask the author to cite them.) ;-)