Hi @Rajesh Jha,
Per my test, if you want to comment on a file, you will need at least edit permission to the file. I feel regretful to inform you that it turns out to be a by-design one. As a workaround, you could require content approval and turn on track changes. Then the person who has to approve the document can accept or reject individual changes once the document comes to them.
You could follow the steps to specify items in a SharePoint library that require approval on SharePoint sites.
- Select Settings , and then Library Settings.
- To open the Versioning Settings page, under General Settings, select Versioning settings.
- In the Content Approval section, select Yes in answer to the Require content approval for submitted items? In the Document Version History section, specify whether you want SharePoint to create versions when a file is edited. You can also choose to limit the number of versions that are retained. In the Draft Item Security section, determine which users can see draft items in the document library.
Here is the document for details
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