Before submitting a manuscript to a journal, it is fairly common at least in my field (psychology) to circulate the manuscript in a limited way to a small number of people who are experts in the area and/or who would be willing and able to provide useful comments, for the purpose of soliciting their feedback and suggestions for improving the manuscript before submitting it for formal peer review.
However it seems that this could lead to a tricky situation if the editor of the journal ends up asking some of those same people who provided feedback to serve as reviewers for the paper, since they will have already read the paper and in a sense "reviewed" it one time already.
So I have two questions about this:
- From the perspective of a person who has been asked by the authors to provide comments, and then later asked by a journal editor to review that same paper for publication: what is your policy, or your perception of the common policy, for what do to here? Do you decline to review the paper because you've already seen it? Do you agree to review the paper, but perhaps provide many of the same comments verbatim as before (at least for the parts of the paper that were not changed), and perhaps let the editor know that you've read it before? Or do you see your prior reading of the paper as totally irrelevant and just approach the review fresh and as normal?
- From the strategic perspective of the authors of the paper, is it better to ask for comments from people who you know are likely to be asked later to review the paper? Or is it better to avoid sending the paper to these people, and instead send it to people who are not as likely to be asked to review the paper but could still provide useful feedback?