Reviewing a preprint can have several benefits, even if the preprint has not yet been formally submitted to a journal. While the specific practices and policies related to preprints can vary, I can provide you with some general insights that may help answer your questions:

Value of reviewing a preprint:

Early feedback and improvement: Reviewing a preprint allows you to provide feedback to the authors before their work undergoes formal peer review. Your insights and suggestions can help the authors strengthen their research, refine their methodologies, and improve the overall quality of the paper.

Speed and accessibility: Preprints offer a faster and more accessible way of disseminating scientific findings. By reviewing a preprint, you contribute to the evaluation and dissemination of knowledge in a timely manner, potentially accelerating scientific progress.

Collaborative opportunities: Reviewing a preprint can also bring opportunities for collaboration. If you find the research interesting, you may reach out to the authors to collaborate on related projects or explore future research opportunities.

Review process after preprint submission:

Formal peer-review process: Although the preprint may have a DOI and be available publicly, it does not necessarily mean it has been submitted to a journal for formal peer review. The preprint may or may not undergo further revisions based on the feedback received during the preprint stage.

Subsequent journal review: If the authors decide to submit the preprint to a journal after obtaining feedback, it will typically undergo a separate review process by the journal's reviewers or editors. The journal may consider the preprint and the feedback received during the preprint stage, but the final decision will be based on the journal's own evaluation.

Availability of reviews and citation impact:

Public availability of reviews: The availability of reviews depends on the specific platform or archive where the preprint is hosted. Some platforms provide a space for public comments and reviews alongside the preprint, while others do not. Check the platform's guidelines to determine whether reviews will be made public.

Preprint rejection and citation impact: If a preprint is rejected by a journal, it does not necessarily invalidate any prior citations it has received. However, the preprint's impact on the scientific community may be reassessed in light of its rejection, and subsequent versions or related publications may be evaluated independently.

Evolving understanding of preprints:

The understanding and practices surrounding preprints continue to evolve within the scientific community. While preprints were traditionally seen as a means of sharing research before formal submission to journals, they are now increasingly recognized as valuable standalone contributions. It is important to stay up to date with the specific policies and practices related to preprints in your field, as they may vary.

Remember, these insights are based on general understanding, and it is always recommended to refer to specific guidelines and policies of the platforms, journals, and communities in which you are involved for a more precise understanding of the preprint review process.